GLOSSARY

In reference numbering convention, a slash symbol is used for two purposes. First, it can be used to list several similar reference numbers (which usually indicate similarity in design or movement) efficiently. For example, Seiko references 6306 and 6309 are almost the same watch and have almost the same reference. Thus they can represented as 6306/9. How many digits one places behind the slash is entirely up to how self-evident it needs to be, at the expense of brevity. When referring to a large family of such references, an 'X' is often used to represent the variable digits. See 'X (reference number)'. The second use of the slash is as a divider to accentuate or add a piece of information. For example, the 0 in Tudor ref.7016/0 indicates that that particular watch was made in steel. Hence, in the case of (vintage) Tudor, ref.7016/0 is not two references but one.

A time convention in which the 24 hours of the day is divided into two halves, the first half from midnight (12:00 a.m.) to noon/midday (12:00 p.m.) denoted ‘a.m.’ and the second half from noon/midday to midnight denoted ‘p.m.’.

A dial that uses 12-hour notation. It must be combined with a 12-hour hand. This is the most common configuration for an analog watch.

A hand that makes a full lap around the dial every 12 hours. It is the standard hour hand.

A notation of timekeeping that indicates the time of day from 12:00 a.m. to 11:59 p.m., based on the 12-hour clock.

A click bezel with 120 positions. The positions align with each hash on the minute track and the space in between.

12 Saphirs. Rolex nomenclature for a bezel set with four sapphires at the hours interspersed with forty-eight diamonds.

A time convention in which the 24 hours of the day starts at 00:00 and ends at 23:59. The 24-hour clock has superior clarity to the 12-hour clock and is used in applications that require brevity and clarity such as hospitals and the military. Hence, it is also commonly called ‘military time’, although there are differences.

A dial that uses 24-hour notation. It must be combined with a 24-hour hand.

A hand that makes a full lap around the dial every 24 hours. This hand is usually used as GMT hand to indicate a second timezone. However, it may also serve as the regular hour hand for a watch with a 24-hour dial.

A notation of timekeeping that indicates the time of day from 00:00 to 23:59, based on the 24-hour clock.

A type of stainless steel very commonly used in the watchmaking industry. Like all stainless steels, 316L is composed primarily of iron, with copious amounts of chromium, nickel, and a small amount of molybdenum and other elements like silicon. The L in 316L signifies that it is a low carbon variant of 316. The lion's share of watch manufacturers use 316L. Manufacturers with more flowery marketing refer to 316L as 'surgical grade steel'. 316L is in fact used widely in the medical industry and maritime industry.

An oscillating mass of an automatic watch that can complete a full 360-degree rotation. This is the opposite of a bumper, which moves within a limited section.

3-color Rolex Cosmograph Oyster. Rolex collecting nomenclature for a ‘Paul Newman’ Daytona chronograph that has three colors on the dial (black and white for the dial and main dial text, red for the DAYTONA text) and has the Rolex signature on top, followed by ‘Cosmograph’ and then ‘Oyster’. These are also known as the ‘Oyster Sotto’ because the Oyster is at the bottom. Also see ‘3CROC’.

3-color Rolex Oyster Cosmograph. Rolex collecting nomenclature for a ‘Paul Newman’ Daytona chronograph that has three colors on the dial (black and white for the dial and main dial text, red for the DAYTONA text) and has the Rolex signature on top, followed by ‘Oyster’ and then ‘Cosmograph’. The authenticity of 3CROC Daytonas is not universally accepted. Also see ‘3CRCO’.

4 Rubis. Rolex nomenclature for a bezel set with four rubies at the quarters interspersed with thirty-six diamonds.

An often pejorative term denoting the ordinances on Swiss origin markings. The term emphasizes that only 60% of costs need be incurred in Switzerland for a watch to be officially 'Swiss', meaning that close to half of the costs may go towards imported components. It is often used to make the point that 'Swiss made' is not a meaningful sign of quality or Swissness.

A click bezel with 60 positions. The positions align with each hash on the minute track.

A type of stainless steel commonly used in the watchmaking industry. Like all stainless steels, 904L is composed primarily of iron, followed by chromium, nickel, molybdenum, and other elements. 904L has a particularly high amount of chromium which gives it a much higher resistance against corrosion and pitting. Despite its being softer than the industry standard 316L, its softness allows it to be polished to a higher degree and its corrosion resistance retains its original luster for longer. For these reasons 904L is used by Rolex.

A watch manufacturer established in Glashütte, Germany in 1845 and revived from communist nationalization in 1990. Abbreviated ‘ALS’ and alternatively written ‘A. Lange & Soehne’ to render the umlaut in the English alphabet. A. Lange & Söhne is owned by Richemont.

(Latin) Ante meridiem. The first twelve hours of the day in a 12-hour clock. Starts at 12 a.m. (midnight) and ends at 11:59 a.m.

(German) 'Down'. Empty.

‘Altimeter, Barometer, Compass’. A name for three major functions that are useful for land activities. An ABC-capable watch allows its wearer to understand his/her bearings, elevation, and forecast the weather. Typically a watch that has all three functions are digital quartz watches purpose-built for exploration or combat.

An online watch publication based out of Los Angeles, USA.

(1747-1823) A horologist from Neuchâtel, Prussia and active in Paris, France. Breguet is credited with inventing the gong spring, flat balance spring with overcoil, the first execution of the tourbillon, and countless other aesthetic innovations and technical improvements that heavily impacted the course of timekeeping and horology.

A measurement of the difference between time kept by a timepiece and real time. The latter is usually represented by the most accurate timepiece available, which in our age would be atomic clocks. In the most practical sense accuracy simply refers to the consistency of the timekeeping component such as the oscillations of a balance or vibrations of a quartz crystal. Accuracy is measured by number of seconds deviated (in positive or negative notation) over a certain period of time. The most common is [+/- n seconds per day].

A thermoplastic also known as poly(methyl methacrylate). It is also known by its many commercial names like plexiglas, acrylite, perspex, and hesalite. It rates a 3 on the Mohs hardness scale. Acrylic crystals are common in vintage watches. While some think acrylic is inferior to mineral and sapphire because of its softness, acrylic is loved by many for how it interacts with light, its warmth, and variety of shapes. Acrylic also possesses many practical advantages. It is highly break-resistant and impact-resistant, and does not shatter. The small scratches and dents it picks up due to its softness can usually be buffed out easily.

A hole in a strap for a pin/tang/ardillon. A strap will usually have six or more of such holes to accommodate different wrist sizes as well as periodic changes in wrist size due to temperature.

A nickname for models of the Omega Genève which feature an anchor at the six o’clock position.

A component that is not manufactured by the original manufacturer. Antonymous with ‘factory’. The term is usually used for easily-replaceable parts that are commonly offered by third-party makers such as crystals, bezels, bracelets, and straps. It is also commonly used to describe diamond settings as aftermarket diamonds command a much lower price than factory diamonds.

A byword for wearing a wristwatch over a cuff. Named after Gianni Agnelli, Italian industrialist and senator who was famous for wearing his watches over the cuff. See 'watch over cuff'.

(French) Apple hands. Invented by Breguet’s master Jean-Antoine Lépine, they were the original ringed hands that influenced the Breguet hands.

A striking complication that sets off an alarm at a designated time. Most alarms work by releasing spring-stored power into a hammer which strikes a membrane. The alarm will run for either a preset time or until power runs out. Many alarms possess a secondary spring solely for the alarm complication instead of drawing power from the mainspring.

A nickname for the Omega Chrono-Quartz reference ST396.0839. The name comes from the shape of the cal.1611’s twin battery contacts (the metal holders that retain the coin batteries) resemble a bird with outstretched wings. The same watch is also called the ‘Montreal’ and the ‘Olympic’.

A nickname for a white variant of a normally other-colored dial. Famous Albinos include the Rolex Explorer I ref.6610 Albino and the Omega Speedmaster Professional ref.3593.20.00 Albino.

The alignment of the different components of the dial to each other. When alignment is poor, the hour markers may not be aligned with the minute track or the dial itself may be askew.

A mechanism in a striking movement which disarms or blocks the cadrature if there is not sufficient power reserve to sound the next chime. It is usually in the form of a spring lever which obstructs the repeater works until the slide is fully pulled. All-or-nothing mechanisms prevent the watch from being misunderstood by the wearer in case the chime is cut off by insufficient power.

A style of hands distinguished by a rapid taper from a skinny base to the shoulder and a gradual taper from the shoulder to the tip. An alpha hand resembles a spearhead where the base resembles the socket, the shoulder the transition, and the rest of the hand the blade. For this reason they are also called ‘lance hands’. Alpha hands may be lumed or unlumed.

Military timezone name for UTC-1.

An instrument that measures altitude. Altimeters can be useful for land exploration, especially for mountaineering.

The rotation angle of a single semi-oscillation of the balance. The balance wheel attached to the balance spring spins in an incomplete circle in one direction and then swings back in the other direction. Each spin is called a semi-oscillation, which also constitutes a single beat for the movement as each spin provides an input to the escapement. The amplitude of a movement is how far, in degrees, the balance wheel swings. Amplitude is often correlated to the health of the movement and should be neither excessive or insufficient.

Analog-digital. A watch that has both analog and digital displays. While many mechanical watches that have a digital display also have an analog display (usually for the seconds which can be difficult to engineer digitally in a mechanical movement), this term mostly applies to quartz watches with an LCD (sometimes LED) and an analog handset. This does not count if the hands are displayed on an LCD screen.

A nickname for the Omega Seamaster reference 145.023, a tungsten-cased chronograph with a colorful dial. The name is a reference to the popular science fiction franchise Star Wars. The nickname ‘Anakin Skywalker’ was dubbed by renowned collector Chuck Maddox as it was the appropriate name for the original, non-PVD version of the black 145.0023 ‘Darth Vader’. In Star Wars lore, Darth Vader is the name of Anakin Skywalker after he turned to the Dark Side much like how the ref.145.0023 and the ref.145.023 are essentially the same watch but in opposite colors.

A display which uses hands to tell the time. Antonymous with 'digital display'.

A watch with an analog display. Antonymous with 'digital watch'.

An escapement for pendulum clocks that utilizes the swinging motion of the pendulum to lock and unlock the escape wheel. The 'anchor' is a component shaped like an upside-down boat anchor. The shank (shaft) of the anchor is connected to the swinging pendulum while the arms of the anchor each has a claw called a pallet. The swinging motion of the pendulum makes the pallets catch and release the sloped teeth of the escape wheel. With this mechanism, the speed of the pendulum controls how fast the escape wheel turns. A simple but highly effective mechanism, the anchor escapement is common in pendulum clocks.

A governor for a striking train which employs an anchor escapement to regulate the strike tempo. The pallets on the anchor lock and release the escape wheel which controls the unwinding speed of the repeater mainspring.

(French) ‘Anchor’. Although it can refer to any anchor-shaped component, it almost always refers to the pallet fork. See ‘pallet fork’.

(Korean) A hemispherical sundial designed in 15th century Korea as an affordable and mass-producible alternative to the more sophisticated striking clepsydras of the era. Angbuilgus were cast in bronze and varnished black with inlaid silver for the markings. They were capable of telling the time as well as the seasons and 24 solar terms.

(French) Chamfering.

See ‘faceted lugs’.

A calendar complication that accurately represents the lengths of all months except February. In terms of ability it is between a simple calendar which must be manually adjusted five times every year and a perpetual calendar which must be adjusted three times every four centuries. Annual calendars provide most of the functionality of a perpetual calendar at a much lower cost and simpler, more reliable engineering, which makes them a popular choice.

A designation for a timepiece with an unsigned dial and unknown brand. Anonymous dials overlap somewhat with sterile dials, but the terms differ in usage. Anonymous dials must be unsigned with no information of the original manufacturer or brand - hence, they are sterile dials with an unclear origin. As anonymous watches usually still have signed movements, they are often called by their movement makers. E.g. ‘anonymous chronograph with Valjoux 22’ or ‘anonymous Valjoux 22 chronograph’.

A cutout in the dial which reveals what is underneath. Synonymous with 'window', although the term 'aperture' is slightly broader. Apertures can reveal a disc which displays the date, day, or simply expose a part of the movement.

A nickname for certain examples of the 11652X series Rolex Oyster Perpetual Cosmograph Daytonas with a minute font spacing error. This error makes ‘Cosmograph’ look like ‘COSMOGR APH’, hence the name ‘APH’.

A component is applied when it is finished separately and attached to the dial surface. It may also be called 'raised' or 'appliqué'.

A type of numerals commonly featured on watch dials, also called Hindu-Arabic numerals or Ghūbar numerals. Arabic numerals are the most widely used number symbols in the world and are commonly found on watch dials, especially those made for high legibility. Not to be confused with 'eastern Arabic numerals'. Sometimes Arabic numerals are called 'western Arabic numerals' to intentionally distinguish them from their eastern counterparts.

An axle or shaft on which gears such as wheels and pinions are mounted. The term also refers to the axle of a mainspring barrel to which an end of the mainspring is attached.

Short for ‘extract from the archives’.

See 'pin'.

See 'pin buckle'.

A nickname for the Seiko reference H558 ana-digi quartz diver as well as the modern SNJ02X series watches inspired by it. The name comes from bodybuilder, actor, and former governor of California Arnold Schwarzenegger, who wore the watch in the 1987 film Predator.

A style of hands distinguished by an arrow tip. The body of an arrow hand is usually tapered from a wide base to a thin neck. Arrow hands may be lumed or unlumed.

A style of indices/markers in the form of an arrowhead or pointer. Sometimes used interchangeably with ‘dagger markers’, though there is a distinction in that the arrow markers rarely have a flat base.

A style of visual arts, industrial design, and architecture that dominated much of the United States and Europe in the interwar period, particularly during the economic and cultural height that was the Roaring Twenties. Art Deco is an eclectic style that combines a bold and geometric aesthetic language, stylized forms of nature such as foliage and sun rays, and liberally interpreted artistic styles from ancient Egypt, India, China, and Mesoamerica. In essence, Art Deco was an international style that permeated the northern Atlantic and symbolized the West's modern technology, boundless wealth and opulence, resplendent cultural maturity and experimentation, and cosmopolitan trade. In watchmaking, Art Deco had a monumental impact on the design of watches, birthing entire categories of watches like cocktail watches as well as numerous iconic models, numeral fonts, and case designs adored today.

Lugs which pivot on an axis. Articulating lugs can come in many styles. They are helpful in making larger watches more wearable on smaller wrists.

A nickname for the Seiko references 7C46-6009 and 7C46-6010 which have deeply scalloped bezels which somewhat resemble an ashtray.

A scale that measures respirations. The asthmometer uses the basic formula of a tachymeter which measures frequency over a second-defined period. Because its purpose is more specific, the asthmometer specifies how many respirations it is graduated for. If it says five, the wearer will count five respirations immediately after starting the chronograph. The number the seconds hand indicates at the end of the fifth respiration is rate of respirations per minute. Asthmometers are frequently found in medical watches, and almost always accompany pulsometers. They must be accompanied by some sort of chronograph that allows the wearer to start, stop, and reset the seconds hand at will.

A family of complications that concern the movement of astronomical objects. While some may classify calendar complications as a subgroup of astronomical complications because our calendars are based on the movements of the Earth, Sun, and Moon, in common usage astronomical complications focus more on celestial activities that do not affect our common calendar. This may include complications that display sidereal time, equation of time, star chart, planetary positions, and other fantastically complicated celestial information.

A case shape that is asymmetrical. Sometimes a catchall term for all unconventional case shapes.

Two gear tooth profiles in a single tooth cross section that are asymmetrical to each other. In watchmaking, there is a considerable minority of asymmetrical-profiled gears.

(French) A workshop of an artist, artisan, or craftsman. In watchmaking, atelier refers to a workshop that is manned by not only the master craftsman but also several assistants.

(French) A factory or workshop which only assembles, times, and cases as opposed to producing any components or dealing with business and logistics.

A category of wristwatch designed for a specific sport. They are not as well-known as very few sports require dedicated timepieces. While there have been many historical designs for watches designed to withstand the shocks of intense sports, modern athletic watches are often born out of sponsorship deals with teams or star athletes. They are built of strong and lightweight materials with particular attention to shock resistance. Some have complications that assist with scorekeeping.

A nickname for the Seiko 5 Sports SKZ2XX series expedition watches. The nickname likely comes from the watch's ability to assist in land navigation and map-reading. It is also known as the 'Landshark'.

A timepiece that measures time by monitoring the resonant frequency of atoms. Atomic clocks typically use cesium, rubidium, hydrogen, or strontium atoms with cesium’s only stable cesium-133 isotope being the most common choice. The typical atomic clock counts 9,192,631,770 vibrations of a cesium-133 atom when exposed to microwaves of the equivalent wavelength (9 GHz). The microwave wavelength is made accurate via a coupled quartz oscillator which is jolted to the correct frequency if the clock’s internal mechanism detects that the wavelength is off. An incorrect oscillator frequency leads to an incorrect microwave wavelength, meaning that the cesium atoms will not become excited. This means that the detector will not pick up the fluorescent signature of the excited atoms, leading to the jolt of electricity that triggers the quartz oscillator to return to the collect frequency and its connected microwave emitter to the correct wavelength. This feedback loop is self-correcting, making the clock very accurate.

A watch manufacturer established in Le Brassus, Switzerland in 1875. Audemars Piguet is privately owned.

(German) 'Up'. Full Power.

A distributor/retailer of watches that is officially sanctioned by the manufacturer to sell their watches to consumers. ADs can give discounts, deals, accessories, warranty, maintenance and repairs, and other services offered by the original manufacturer in addition to their own benefits. This distinguishes them from non-authorized dealers such as private sellers, second-hand sellers, and others who don't represent the manufacturer.

A movement which can be wound with an oscillating mass. Synonymous with 'self-winding movement'. Automatic movements convert the wearer's wrist activity to potential energy by using the rotor-weight to wind a spring (in a mechanical watch) or capacitor (in a quartz watch). Many automatic movements can also be manually wound. While automatic movements are usually mechanical, there are also many electronic movements that utilize automatic mechanisms to charge electrical capacitors. In the latter case, 'self-winding quartz', 'automatic quartz', or 'autoquartz' is used to distinguish these movements from the better-known mechanical automatics.

(French) Advance. Commonly written in full or abbreviated as 'A' on balance cocks for adjusting the regulator. Pointing the index towards A speeds up the watch.

(German) Short for 'Beobachtungsuhr', or 'observation watch'.

A nickname for the Seiko SARB03X series watches which have high quality finishing and resemble Grand Seiko sports watches, featuring similar dauphine hands, baton markers, case profile, bracelet, and dial composition.

A nickname for the Seiko references 6139-7030/1 and 6139-7070/1 which closely resemble the 6138-300X series ‘Jumbo’ watches.

A nickname for the Seiko reference 6138-8030 which closely resembles the 6138-003X ‘Kakume’ series. One of the dial configurations of this reference is called the ‘John Player Special’ after the famous Rolex wristwatch which also sports a black and gold color scheme.

A nickname for the Seiko reference 6138-8000 which closely resembles the 6138-8020 ‘Panda’. Like the Panda, the name ‘Baby Panda’ is derived from the look of the most famous watch that carries the reference and applies to all other dial configurations even if they are not panda dials. The famous Seiko ‘Reverse Baby Panda’ is also part of this family.

The gaps or clearance between parts, particularly meshing gear teeth. Backlash is an important concept in watchmaking as the majority of wheels and pinions in a mechanical movement require a certain degree of backlash. In the absence of backlash, meshed wheels may jam and clutches may not engage. On the other hand, excessive backlash means that the watch will run too loosely, leading to unstable operation of moving parts, accelerated wear, and a general loss in reliability and accuracy.

A light that illuminates an LCD from the back or side. Unlike LED displays, LCDs do not produce their own light and thus must be illuminated by an external light source to be read at night.

A device that is the timekeeping organ of a mechanical movement. The balance consists of a weighted wheel (balance wheel) and a spiral or helical torsion spring (called the 'balance spring' or 'hairspring') mounted at the wheel's center axis which allows it to rotate back and forth, or oscillate at a consistent frequency. This frequency, also called the 'beat' of the watch, allows the watch to keep time reliably. The balance's motions controls the rotation of the gear train via the escapement. Balance can also be short for 'balance wheel'.

A double-ended bridge that mounts the balance at its center. A balance bridge is anchored to the main plate on both ends unlike a balance cock which is anchored at only one end. Essentially a balance bridge is two conjoined balance cocks.

A single-ended bridge that mounts the balance at its end. A balance cock is anchored to the main plate on only one side, with the other suspending the balance. Compare with 'balance bridge'.

Also known as a hairspring. A spiral or helical torsion spring that allows the balance wheel to oscillate at a consistent frequency. The balance spring starts at the collet and terminates at the stud. Not to be confused with 'mainspring'.

The axle on which the balance wheel is mounted.

A spoked wheel that is weighted in order to oscillate at a consistent frequency with the assistance of the hairspring. A balance wheel may have different types of weight which control its oscillating rate and adjusts for factors such as temperature.

A three-link bracelet consisting of one extremely wide but short center link and two narrow and short outer links, and a sliding clasp. The center links have spaces between them that allow a hooked beak in the sliding clasp to latch on. The bracelet was likely first made by American company Krementz & Co., which saw little success compared to an identical product sold by B. H. Britton & Sons as the 'Bonklip'.

A component of a wristwatch that fastens the watch to the wearer's wrist. A band constructed of a pliable material such as leather, fabric, or rubber is often called a 'strap' while one constructed of metal parts is usually called a 'bracelet'.

See ‘banking pin’.

A pin which limits the range of motion of the pallet fork. Banking pins always come in pairs.

A nickname for the unique Rolex Oyster Perpetual reference 6062 Triple Calendar in yellow gold with a gilt black dial with diamond indices specially made for the last emperor of Vietnam, Bao Dai (r. 1926-1945).

A component of a wristwatch that fixes the strap to the head, usually between the lugs. By far the most common type of bar is the spring bar.

A style of indices/markers in the form of a rectangle. Somewhat used interchangeably with ‘baton markers’.

A texture with thin, shallow striations that resembles the bark of a tree. The term is most closely associated with Rolex watches, some of which featured bark texture on the bezel and bracelet center links.

An instrument that measures atmospheric pressure. Barometers can be useful for determining elevation in the absence of a dedicated altimeter and for forecasting the weather.

A hollow cylindrical container which houses the mainspring. The cavity of the barrel has enough space for the mainspring to be uncoiled and its circumference is lined with teeth to interact with the gear train and deliver power to the movement. A watch may have more than one barrel - and thus more than one mainspring - to increase its power reserve.

See ‘tonneau case’.

A nickname for Rolex dials featuring a particularly fat crown resembling the head of Simpsons character Bart Simpson. The Bart Simpson dial marks the final iteration of the Rolex Oyster Perpetual Submariner references 5512 and 5513 to feature gloss gilt dials.

A time scale used in astronomy to calculate the positions and motions of celestial objects within the solar system, measured relative to the barycenter (center of mass) of the solar system. TDB accounts for relativistic effects caused by the gravitational influence of the Sun and other planets, making it ideal for astronomical calculations for celestial bodies. TDB is closely related to Terrestrial Time (TT) but includes periodic relativistic corrections to synchronize with the solar system’s center of mass.

A nickname for the Rolex Oyster Perpetual GMT-Master II reference 126710BLNR, a GMT-Master II with a black and blue Cerachrom bezel, blue GMT hand, and Jubilee bracelet. The name arose out of a need to differentiate it from its predecessor whose only cosmetic difference is the bracelet.

A nickname for the Rolex Oyster Perpetual GMT-Master II reference 116710BLNR, a GMT-Master II with a black and blue Cerachrom bezel, blue GMT hand, and Oyster bracelet.

A style of hands distinguished by long and slender hands with little or no taper. The tips of baton hands may be rounded or pointed. Baton hands may be lumed or unlumed.

A style of indices/markers in the form of a rectangle. Somewhat used interchangeably with ‘bar markers’.

A device that converts chemical potential energy into electrical energy. Batteries store energy in electrochemical cells, leading to slower charge and discharge times, steadier voltage, and longer-lasting discharge than a capacitor. Batteries may either be primary (single-use) or secondary (rechargeable). Batteries are the most common power source for electrically-powered watches. Some light/solar-powered watches use rechargeable batteries instead of capacitors. Also see ‘capacitor’.

A style of visual arts, industrial design, architecture, and cultural movement spearheaded by the Staatliches Bauhaus in interwar Germany. Bauhaus epitomized the marriage of practical function and aesthetic beauty, imbuing functional objects with an uncluttered design with a reserved artistic flair that maximized their utility while also being beautiful. While short-lived and disorganized, Bauhaus had a tremendous influence on our world and continues to live on to this day. In watchmaking, Bauhaus is credited with the creation of the modern wristwatch as we known it as well as dial, case, and font designs that are ubiquitous even today.

Any style of Arabic numerals done in a Bauhaus fashion. While there isn’t one representative numeral font that speaks for Bauhaus, the ones used in watch design share a few key characteristics: sans-serif, light to medium weight (thickness of stroke), simplicity, and lack of embellishment.

A watch manufacturer established in Geneva, Switzerland in 1830. Baume & Mercier is owned by Richemont.

A type of caseback that is fastened by flanges on the caseback locking into notches in the caseback opening. The mechanism is most reminiscent of a camera lens locking onto a DSLR body and somewhat similar to how a bayonet's notch engages with the bayonet lug at the end of a rifle. Bayonet casebacks are essentially screw-down casebacks with much beefier and shorter threading, which offers the security of the threaded caseback while preventing the possibility of cross-threading. Therefore they are excellent choices for dive watches. Bayonet casebacks frequently accompanied vintage Super Compressor dive watches but can still be found in many famous modern dive watches under various branded names.

A type of abrasive blasting that blasts glass beads on a surface. The resulting finish has more sheen than the oft-compared sand-blasting.

A bracelet made of many small, vertically long, and horizontally narrow links that resemble grains of rice. They may be purely constructed of these links or have slightly differently-shaped outer links. Beads-of-rice bracelets were first constructed by Gay Frères. Due to their versatile look they are common choices for dress watches as well as dive watches.

A style of lugs that are straight lugs with a small curve towards the wrist, making the sides of the lugs resemble beans. Also see ‘fagiolino’.

A nickname for the Audemars Piguet Royal Oak Offshore reference 25721ST. The name is a reference to its massive dimensions and weight. Later on all Royal Oak Offshore watches with a chronograph would be called Beasts.

A semi-oscillation of a balance spring. It is so called because of the sound that the balance makes when reaching the end of its range of motion. A beat is important in mechanical watchmaking as it is counted to measure the frequency of a watch.

The time difference between beats, or semi-oscillations in a mechanical balance. It is measured in milliseconds (ms). The ideal beat error is 0, as it is ideal for each beat to immediately succeed the previous beat.

A measurement of how many times the balance semi-oscillates, or ‘beats’, over a certain period of time. It is a common way to indicate the frequency of a mechanical balance. Beat rate is usually indicated as beats per second (bps), beats per minute (bpm), or per hour (bph). It can alternatively be measured in vibrations, which is completely interchangeable with beats. Also see ‘Hz’ and ‘vph’. Not to be confused with ‘rate’.

A watch that is intended to be worn even at the risk of taking damage. Beater watches are typically chosen from exceptionally durable watches that can handle abuse. Many beaters are affordable to the owner as there is a higher risk that the watch may be damaged beyond repair or lost. This is not always the case as some watches command high prices for the same reasons they would be ideal beaters. Beaters should not be confused with throwaway or disposable watches.

A nickname for the Audemars Piguet Royal Oak Offshore reference 25721BA. As the ref.25721BA was the first all-gold Offshore, it contrasted greatly with the steel original dubbed the ‘Beast’. Therefore the gold watch was nicknamed ‘Beauty’. Also see ‘Pounder’.

An article of watchmaking furniture that is used as a work surface for watchmakers. Benches are usually elevated to the watchmaker’s upper chest level to minimize hunching, and often have padded arm rests. Many come with drawers and cabinets to store to numerous tools and spare parts required for watchmaking.

(German) Literally 'observation watch'. Commonly abbreviated as 'B-uhr'. In common English usage the term refers to a type of pilot's watches issued to certain members of the German Luftwaffe in WWII. However in German the term may broadly refer to a wide range of observation watches and clocks used for navigation and precise timekeeping. Also see 'Tensoku'.

A nickname for a variant of the Rolex Oyster Perpetual Submariner 16610LV ‘Kermit’ with a bezel of a lighter hue of olive green than standard. The nickname comes from the renowned brand of olive oil. On a side note, all Bertolli Kermits feature the ‘Flat Four’ because they were all produced before the Flat Fours were discontinued by a font redesign. Also see ‘Flat Four’.

A gear with slanted teeth arranged across a conical pitch surface. Two meshed bevel gears arranged perpendicularly are capable of transmitting mechanical power from a horizontal to vertical shaft or vice versa. Though not common in watchmaking, certain movements make use of bevel gears. Also see 'crown gear', which is a similar gear which transmits power to a perpendicular axis.

The ring that frames the crystal of a watch. The bezel's function is sometimes to fasten the crystal of the watch, but may also serve other or additional functions such as protecting the crystal from impact, timing events, calculations, or decoration.

A ring-shaped component that fits onto a bezel to give the bezel color, a scale, or markers. A bezel insert can be identified by its having a different color or material from the outer rim of the bezel, e.g. a black stainless steel bezel or a ceramic bezel that is surrounded by a stainless steel bezel rim. Some watches have entire bezels made out of a different material (e.g. ceramic or gold) while others have markings directly engraved into the bezel. In these cases, the watches do not have bezel inserts.

'Big Fucking Kinetic'. A nickname for the Seiko SKA3X1 Kinetic divers, known for their large and chunky size.

A bezel, usually rotating, consisting of two colors. Bi-color configurations are commonly used for GMT bezels which distinguish between day and night hours and for diving bezels which often color the first fifteen or twenty minutes (a common dive time for dives at 30m below the surface).

In casual parlance, ‘bi-compax’ refers to a watch - typically a chronograph - with two sub-dials. While this usage is now common, it’s technically a misnomer. Refer to ‘Compax (general)’ and ‘Compax (Universal Genève)’. The original creator of the Compax name never made a Bi-compax, but if it did it would have three sub-dials.

A bezel which rotates in both directions. Bidirectional rotating bezels are the norm for rotating bezels other than most diving bezels.

A 360-degree rotor in an automatic watch that spins and winds in both directions. Also see ‘unidirectional rotor’.

A nickname for the Tudor Oysterdate chronographs of the 9400 and 79100 series. The name comes from the watch's large and blocky case to accommodate the automatic chronograph movement.

A nickname for the Omega Seamaster Planet Ocean GMT reference 215.92.46.22.03.001, which is a big and blue watch.

A nickname for the Rolex Oyster Perpetual Submariner references 6200, 6538, and 5510 owing to their oversized crowns which measure 8mm. Their large crowns were further accentuated by their lack of crown guards.

A nickname for a watch, especially a chronograph, with particularly large sub-registers. Famous big eye chronographs include models produced by Longines, Rolex, Universal Genève, and Enicar.

A nickname for Rolex Daytona dials with larger-than-normal sub-registers, found on references 6263 and 6265.

A nickname for the Rolex Cosmograph Daytona reference 6263 with an extra-large 'Daytona' written in red ink above the hour sub-register.

A nickname for variants of the Omega Seamaster 300 reference 165.024 sporting a large triangular lume plot for the 12 o’clock marker.

A balance wheel that is constructed of two different metals, usually brass for the outer layer and steel for the inner layer. The bimetallic composition allows the balance wheel to maintain a steady rate of oscillation in both hot and cold temperatures due to the different temperature coefficients of the two metals. Hairsprings tend to expand and contract depending on the temperature and brass reacts similarly, making them compatible for each other. The steel inner rim provides stability as pure brass would be too unstable and unreliable for timekeeping. Also called a 'self-compensating balance wheel'. As a bimetallic balance wheel has two cuts to allow the balance wheel arms to expand and contract, it is also called a 'split balance wheel'.

A nickname for the Seiko reference 7A28-6000 and its reissue, SCED019 which was worn by Lance Henriksen as the android Bishop in the 1986 film Aliens. While the watch is sometimes called 'Giugiaro' after its designer, this name is taken by the more famous gray variant 7A28-7000 worn by Sigourney Weaver as Lieutenant Ripley.

A method of finishing and type of polishing where the metal surface is rubbed to such a smooth finish that the surface appears jet black from certain angles. Also known by its French name 'spéculaire' and as 'mirror polish' and 'block polish'. Black polish is laborious and difficult and thus typically associated with high horology.

See ‘Peter Blake (Omega)’.

A watch manufacturer established in Villeret, Switzerland in 1735 and now headquartered in Le Brassus, Switzerland. Blancpain is owned by the Swatch Group.

A hole that does not completely penetrate and therefore has only one entry point. In watchmaking, a blind hole refers to a lug hole that does not extend to the outside surface of the lug. In this context it is antonymous to ‘drilled lug’.

(German) ‘Flashing seconds’. See ‘foudroyante seconds’.

Bleu, Noir. Rolex nomenclature for a blue and black bi-color bezel.

A component of a chronograph mechanism which acts as a brake for the chronograph runner/chronograph wheel which controls the chronograph seconds and by extension the rest of the chronograph hands. The brake is a lever which is applied to the runner in its default state and can be lifted by

In Rolex collecting nomenclature, a Bloodstone dial is a jasper dial with specks of red from inclusions of hematite. It is featured on the reference 18038 Day-Date.

Bleu, Rouge. Rolex nomenclature for a blue and red bi-color bezel.

A nickname for the Rolex Oyster Perpetual GMT-Master II reference 1675 with a blue bezel. The watch was allegedly ordered for the United Arab Emirates Air Force. There is a substantial number of experts who believe that Rolex never made such bezels. The authenticity of the watch remains one of the most controversial and unresolved mysteries in the Rolex world to this day.

A nickname for the Rolex Oyster Perpetual Submariner references 16613, 116613, and 126613LB which feature a blue dial, blue bezel, and two-tone case.

A dial configuration of the Rolex Datejust that features applied stylized Arabic numerals around a railroad chapter ring on an enamel dial. The Boiler Gauge is easily distinguishable by its quirky numeral font and its chapter ring which lies inside the ring of hour markers. The latter gives it its nickname as it resembles the steam pressure gauge of a boiler.

A nickname for various Rolex Oyster Perpetual references in the mid-20th century that have bombé, or out-turned/twisted lugs. ‘Bombay’ is either a corruption or humorous misreading of ‘bombé’. Also see ‘bombé lugs’.

(French) Bomb lugs. Another name for ‘twisted lugs’. The etymology is unclear.

Any watch or watch accessory associated with the fictional MI6 agent James Bond may be referred to as a ‘Bond’. Common items associated with James Bond include the Bond nato strap, Bond bracelet for the Omega Seamaster, and several Rolex, Omega, and Seiko watches.

A Bond Omega generally refers to any Omega Seamaster that was worn by an actor playing the fictional MI6 agent James Bond in a canon film. In a narrow sense, it refers to Seamasters that share design language with ‘the’ James Bond Seamaster reference 2541.80.00 - sporting a scalloped rotating bezel, skeletonized hands, aluminum bezel insert, and a five-link stainless steel bracelet. These include references 2531.80.00 and 2220.80.00 that were featured in Bond films from Tomorrow Never Dies to Casino Royale as well as their quartz and mid-size variations not featured in the films. The term in the narrow sense does not refer to the Planet Ocean, Seamaster 300, and Seamaster 300M watches that were also worn by Bond in subsequent films.

A nickname for a style of five-link bracelet fitted to the Omega Seamaster, named after the fictional MI6 agent James Bond due to its appearance in the first Bond film featuring a Seamaster. The bracelet has three brushed links on the edges and middle, and two narrow links with polished edges between the brushed links.

A style of nato strap featuring two vertical stripes running along the length of the strap. The name comes from a nylon strap that was worn by MI6 agent James Bond played by Scottish actor Sean Connery in the 1964 film Goldfinger. The strap was initially a black strap with khaki stripes and burgundy stripe borders, but mistaken for a black strap with gray stripes due to black and white stills.

A type of leather. Bonded leather is commonly understood as the least desirable kind of leather, with many considering it a non-leather product. It is constructed with leather scraps, shavings, and other normally disposed materials and put together with copious amounts of glue and plastic.

A variety of bamboo bracelet patented by Dudley Howlitt of England and manufactured by B. H. Britton & Sons of London. Due to Britton's contract with the British Armed Forces, 'Bonklip' has become a household name as well as a byword for the bamboo bracelet.

Acronym for 'beads-of-rice'. See 'beads-of-rice bracelet'.

A regulator that utilizes an index lever to adjust the curb pins and free length of the balance spring. Invented in 1755, the Bosley regulator is one of the most important and seminal regulator styles and is still widely used today. Most regulator designs are a variation of this system.

A nickname for the Seiko SKA2XX series Kinetic divers, known for their large and chunky size.

A nickname for the Seiko 5 Sports SRPC6X series watches whose flat profile and bezel notches make them resemble a crown cork bottle cap.

Synonymous with ‘bush’.

The protective box that accompanies a watch.

The state of having both the original box that the watch was delivered in as well as the appropriate documentation unique to a watch that has a matching serial number.

A font of extra-bold sans-serif Arabic numerals first named by Ball. The name comes from the Box Car dial introduced in 1925. The font became standard in the railroad pocket watch industry, and many other manufacturers followed with similar designs. The Waltham corporation called their numerals ‘Box Car’ as well, while Hamilton chose the name ‘Heavy Gothic’ and Elgin went with ‘Heavy Arabic’.

A watch designed with a boy or adolescent male in mind. Boys' watches share the design language of men's watches but come in considerably smaller sizes. The term is rarely if ever used today.

Beats per hour. A unit of measurement for frequency in movements with mechanical balances.

Beats per second. A unit of measurement for frequency in movements with mechanical balances.

A band made of metal. Usually a bracelet is constructed of many individual links which makes the bracelet flexible.

A device that extends the wearable length of a wristwatch bracelet. Extenders are useful when the exact extra links are unavailable.

A press that is designed to remove or add the pins and collars to a bracelet.

Military timezone name for UTC-2.

Lugs which have a clear and visible brazing line between the base of the lug and case, or any lugs that are attached through brazing regardless of visibility. Brazing is a metal-joining technique where a molten filler metal of a lower melting point than the workpieces conjoins two unmelted workpieces. Brazed lugs are characteristic of earlier wristwatches of the early 20th century before the lugs could be machined together with the case or the joining techniques became more advanced. They are sometimes erroneously known as ‘blazed lugs’. Also see ‘soldered lugs’ and ‘welded lugs’.

A watch manufacturer established in Paris, France in 1775 and now headquartered in L'Abbaye, Switzerland. Breguet is owned by the Swatch Group.

A dial with Breguet numerals. While a dial with other Breguet signatures such as a grand feu enamel or engine-turned finish may warrant the name, the term most commonly refers to a dial that has Breguet numerals.

See 'Breguet overcoil'.

A style of hands distinguished by a convex shaft with a curved taper, a ring towards the neck, and a triangular pointed tip, The Breguet hand can be considered a type of moon hand. The name originates from the hands' creator, legendary watchmaker Abraham-Louis Breguet. They were slightly modified variations of the 'apple hands', or aiguilles à pomme invented by Breguet's master Jean-Antoine Lépine. Breguet hands are not lumed.

A style of Arabic numerals distinguished by calligraphic strokes of highly varied thicknesses and whimsical curves. Breguet numerals are traditionally painted onto an enamel dial but are also commonly fashioned out of metal and applied. The name originates from the numerals' creator, legendary watchmaker Abraham-Louis Breguet.

A bent, incurved terminal section on a coiled hairspring to improve isochronism in hairspring amplitude. In laymen's terms a Breguet overcoil refers to a hairspring with a bent end that coils over the rest of the concentric coils, which compensates for variations in amplitude and makes the balance run more evenly. Also known as the 'Breguet spiral', 'Breguet hairspring', 'Phillips terminal curve', 'terminal curve', and 'terminal coil'.

A watch manufacturer established in Saint-Imier, Switzerland in 1884 and now headquartered in Grenchen, Switzerland. Breitling is owned by the Partners Group.

(French) Patent.

A nickname for the Audemars Piguet Royal Oak Offshore reference 26470OR. The name is a reference to its immense weight and mega tapisserie dial which looks like a brick wall.

A structural piece of a movement that is fastened to the plate on two ends. A bridge usually has a mounting point towards its center that can suspend a wheel of some sort. Bridges are generally more stable than cocks but occupy more space. Also see ‘cock’.

Brillants. Rolex nomenclature for a bezel set with baguette cut diamonds.

A symbol that is an upwards-pointing tanged arrowhead, abstracted into three isosceles triangles converging at a single apex. In an even simpler form it may simply be three lines. The symbol is derived from a more figurative depiction of the arrowhead which is commonly used as a heraldic device. The broad arrow is used to mark property of the British government, especially the Ministry of Defense. Many watches issued by the British military had the broad arrow printed on the dial and/or engraved on the caseback.

A nickname for the Seiko 5 Sports reference 6139-6010 Speed-Timer automatic chronograph with a black dial, worn by martial arts legend, actor, and filmmaker Bruce Lee. The monicker 'Bruce Lee' is sometimes used more generally to refer to any chronograph in the 6139-601X family, which includes several other color variations.

A method of finishing where a spinning wire brush is used to abrade the surface of metal to create unidirectional lines.

A nickname of the first generations of the Rolex Oyster Perpetual self-winding watches, so named by British collectors because of the bubble-like bulbous caseback designed to accommodate the oscillating rotor. The same watch was nicknamed ‘Ovetto’ by Italian collectors. The first Bubbleback reference is the reference 1858. Also see ‘Ovetto’ and ‘Ovettone’.

A component of a watch band that uses a loop and catch at the end of one piece to fasten the other piece. The buckle is one of the two major locking mechanisms for a band alongside the clasp. It is considered the most classic and simple locking mechanism for a wristwatch. Advantages of the buckle include simplicity, reliability, price, elegance, and ability to lay the watch flat on a surface. Disadvantages include incompatibility with bracelets, heavy wear on the strap material and adjustment holes, and increased risk of dropping the watch when putting it on. Also see 'clasp'.

A Rolex Oyster Perpetual Datejust or Day-Date dial with printed Roman numerals. The name comes from John Buckley, a watch dealer based in New York City who jokingly named these then-unpopular dials after himself as a jab at the haphazard naming conventions of dial configurations. The discussion forums promptly started calling these dials 'Buckley dials'.

A watch and jewelry manufacturer established in Rome, Italy in 1884. Bulgari's watchmaking is based in Neuchâtel, Switzerland. Bulgari is owned by LVMH Moët Hennessy Louis Vuitton.

A nickname for the Seiko references SKXA53 and SKXA55 divers which have indices that resemble rifle bullets.

A style of lugs that resemble a bullet. A pair of bullet lugs resemble two bullets headed in opposite directions, with the flat ends of the bullets accommodating the bar.

A style of indices/markers in the form of rifle bullets, with a flat outer base and a rounded taper towards a sharp tip.

(French) A certification of accuracy issued by an astronomical observatory to a certain movement after accuracy testing. ‘Bulletin de Marche’ can translate to ‘Report of Operation’ or ‘Report of the Running (of the Watch)’. Bulletins de Marche are usually given to a single, serial numbered movement that was actually tested by the observatory.

In watchmaking, a 'bullhead' is any chronograph case that has its crown and pushers at the twelve o'clock position instead of the usual three o'clock position. The case profile is also often tapered, with a wider top end and narrower bottom end, further resembling the head of a bull. The bullhead chronograph can be chiefly seen in the catalogues of Seiko, Citizen, and Omega.

A nickname for the Seiko 6138-004X series automatic bullhead chronographs. Also see 'bullhead'.

A dial configuration that uses concentric circles of different colors to divide the dial space like a target, hence the name. The bullseye dial is similar to the sector dial, but the difference is that the bullseye dial emphasizes a difference in color for design while the sector dial emphasizes a clear separation of the minute and hour markers for legibility. The two are not mutually exclusive and it is common to see bullseye sector dials. Black and white bullseye dials are called ‘tuxedo dials’.

A type of oscillating mass in an automatic mechanical movement that does not make a full rotation. Instead, it travels within a limited section of the circle. The name comes from how the weight bounces or bumps off of springs located at each end of its travel area. Bumpers are sometimes seen as antiquated and are rarely seen in modern watches.

A type of automatic movement which uses a bumper. See 'bumper'.

A style of strap, usually leather, that employs a pad behind the watch that separates the caseback from the wrist. Bund pads are wide enough for the watch head to rest on comfortably and usually have a slit on each end or a loop through which the normal watch straps are pulled through. In the past the bund strap protected a non-water resistant watch from the wearer's sweat while also protecting the wrist from the caseback in extreme heat or cold. This was especially useful for tankers and aviators. However, the bund strap is usually a style choice.

A nickname given to various watches associated with the army of the Federal Republic of Germany (Bundeswehr). The name is most commonly associated with two-register chronographs with rotating timing bezels manufactured by Heuer, Leonidas, Sinn, and others.

A nickname for the Seiko reference H556-5050 ana-digi alarm chronograph worn by Paul Reiser as Carter Burke in the 1986 film Aliens.

A tool with a smooth surface that is used for polishing fine surfaces such as screw heads or studs.

A circular piece of (usually) brass that is intended reduce friction between a pivot and its hole by serving as the hole’s lining. Bushes often fulfill similar roles as pivot jewels but are cheaper and more resilient to damage. However, bushes are more susceptible to wear, which leads them to be used for pivots that do not rotate as much.

Synonymous with ‘bush’.

Slang for a watch with an aftermarket diamond-setting job. It is antonymous to ‘factory’ in this context.

See ‘Morpho’.

Another word for a double-fold clasp. Its name comes from how the clasp opens on both sides like a butterfly spreading its wings. Also see 'double-fold clasp'.

A small compass in the shape and size of a large button that is meant to be attached to a watch band. Button compasses have been common accessories for alpinists, soldiers, navigators, and explorers due to their convenience. While not as accurate as full-sized compasses, button compasses are easily accessible. They are also loved for their aesthetic.

A style of jeweled crown distinguished by a cabochon, or a polished and unfaceted jewel.

(French) Also known as 'under-dial work' in English. Mechanisms and clockwork for a specific purpose, especially for repetitions. In modern usage it is treated as a somewhat antiquated synonym for 'module'.

A nickname for the Seiko references SNDA13/15 (quartz) and SKA383/385 (Kinetic) divers whose huge case size probably granted them the nickname 'Caesar'.

The Spanish adaptation of Arabic 'Qal'at Rabah', or 'Fortress of Rabah'. Calatrava is where the Spanish repelled the Moors in 1158, prompting the establishment of the Order of Calatrava symbolized by the Calatrava Cross. In watchmaking, this name is famous due to Patek Philippe. Also see 'Calatrava Cross', 'Calatrava (wristwatch)', and 'Calatrava (style)'.

An unofficial catchall name for a group of wristwatches that reflect the design features of the Patek Philippe Calatrava wristwatch. It refers particularly to the case design, namely a case with a thin profile, slab-sided flanks, gently tapering lugs naturally sprouting out from the case flanks, and a simple round bezel. Also see 'Calatrava (wristwatch)'.

A family of wristwatches manufactured by Genevan watchmaker Patek Philippe. Launched in 1932 as the reference 96, the Calatrava is one of the most influential wristwatch designs in history. The Calatrava was designed with Bauhaus principles and pioneered gently tapering integrated lugs that flow naturally from the case flanks and a round dial with practical and legible markings. In an era where wristwatches were relatively new and many designs were simply afterthought modifications of small pocket and pendant watches, the Calatrava set the blueprint for wristwatch design forever and remains a universally respected icon of quietly elegant design. Also see 'Calatrava cross' and 'Calatrava (style)'.

A type of cross, in the form of a Greek cross with a fleur-de-lis at each end. It served as a symbol of the Order of Calatrava, a Spanish religious and military order. In watchmaking it is famous as the symbol of watchmaker Patek Philippe, and as an eponymous family of dress watches produced by the company. Also see 'Calatrava (fortress)', 'Calatrava (wristwatch)', and 'Calatrava (style)'.

A system of organizing periods of time, typically into days, weeks, months, years, etc. See ‘calendar complications’ for the application of calendars in watchmaking.

A family of complications that concern the tracking of days, weeks, months, years, and other units and periods of time in the human calendar. This includes simple complications like a date complication and high complications like perpetual calendars.

In watch collecting parlance, a California dial may refer to a refinished or fake dial. This is in reference to a famous dial refinisher in California - probably Kirk Rich Dial Co. - which refinished many damaged or aged dials. As the name has caught on to refer to the Rolex error-proof dials, this use is not as common as once was. Also see ‘Texas dial’.

A style of indices/markers that combine Roman and Arabic numerals, typically for each half of the dial. In official Rolex nomenclature it was dubbed the ‘Error-proof dial’ to emphasize its allegedly superior legibility. The California nickname is somewhat controversial as some believe it was a derogatory name for refinished dials (most famously refinished in California) while others maintain that the association simply arose from the dial’s popularity in the state.

A device used to measure the dimensions of an object. Most calipers in modern watchmaking are vernier calipers. Calipers are used to measure important dimensions on a watch like lug width, lug-to-lug, case diameter, dial diameter, buckle width, etc.

A GMT that has an independently-adjustable GMT hand. This configuration is useful to people for whom local time is home time (i.e. they are in their home time zone) but need to read the time of a second time zone for business calls or contact with family, hence the name 'caller' or 'office' GMT. The caller GMT is not as suited for traveling compared to the traveler GMT as adjusting the regular display to the local time requires the watch to be reset. While the wearer can use the GMT hand to reference local time, it is more difficult to read. Also see 'traveler GMT'.

A rotating piece that transforms rotary motion into linear motion.

A chronograph which utilizes a shuttle cam or a similar system as its control system. Cam chronographs are far simpler than the column wheel chronographs before them and are reputed to be more rugged and reliable, cheaper to manufacture, and more tolerant to manufacturing irregularities. With modern manufacturing technology, the difference in reliability between column wheel and cam chronographs have been reduced. This has also brought significant improvements to the previously rougher pusher feel of cam chronographs, further leveling the two. Therefore, cam chronographs are often chosen for their cheaper manufacturing cost and simpler mechanics. Also see ‘column wheel chronograph’ for comparison.

A balance wheel that is adjusted with disc-shaped inertia weights which are also called inertia blocks or masselottes.

See ‘carriage clock’.

A name for early wristwatches that were used in the British colonial campaigns of the late 19th century and the First World War.

A component of the motion work which is mounted on the central axis of the watch (the center stack) and translates the movements of the wheels to the hands. It is directly controlled by the second wheel of the movement and thus completes a rotation every hour. Hence, the minute hand is directly mounted to the cannon pinion. The cannon pinion also indirectly controls the hour hand via a reduction drive called the 'motion work'. The cannon pinion is made up of a hollow shaft or pipe with a pinion fused to the base. The shaft is fitted to the center wheel arbor. Its name comes from the appearance of its long hollow shaft which resembles the barrel of a cannon. Also see 'motion work'.

A crown with a removable cap that resembles a cask or water canteen. The cap is threaded to screw down over the crown and is typically tethered to the side of the case via a chain. Canteen crowns bolster water resistance and protect the crown from shocks. They were popular in mid-20th century dive watches and gradually became obsolete with evolving water resistance technology. Today they are used primarily for their distinctive look.

See 'gold-capped'.

A device that stores electrostatic energy by accumulating charges on an electrical field in the form of thin sheet metals separated by dielectric insulators. Capacitors store electrostatic energy in electrical form, leading to much faster charge and discharge speeds than a battery which contains potential energy in chemical form which must be converted to electrical energy. In watchmaking, capacitors are used in many rechargeable electrically-powered watches such as automatic quartz and light/solar-powered watches. Also see ‘battery’.

A nickname for the Seiko reference 6105-8110 diver and its various modern reissues. The watch was worn by Martin Sheen as Captain Benjamin Willard in the 1979 film Apocalypse Now, a reflection of the fact that American soldiers in Vietnam often wore the 6105. The 6105 is also called the 'Uemura', after a Japanese explorer. See 'Uemura'.

A case shape distinguished by a horizontally long oval profile.

In watchmaking, a carillon is an assortment of hammers and gongs which is capable of making at least three distinct pitches. This can be achieved with having three gong springs each tuned differently, or by having differently tuned hammers striking the same gong spring. Carillons are rare in watchmaking as only two pitches are needed to make three distinct sound signatures (dong, ding, ding-dong), but are highly valued for their ability to play complex chimes such as the Westminster chime.

(French) A square case.

(French) Curved square. A case shape which is more-or-less a square or stout rectangle with rounded edges. Several carré galbé cases feature subtle inward curves on the case flanks. In Italian, this case style is often called ‘cioccolatone’.

A clock style with a box (traditional) or cylindrical profile, footed base, and a carry handle. Invented by Abraham-Louis Breguet for Napoleon for his military campaigns, this style of clock is also called the ‘campaign clock’.

A watch and jewelry manufacturer established in Paris, France in 1847. Cartier's watchmaking is based in La Chaux-de-Fonds, Switzerland. Cartier is owned by Richemont.

A component is carved when it is carved, etched, engraved, or otherwise cut into the dial surface.

The housing of all the components of a clock. Cases are usually crafted out of a metal.

A soft surface for a watch to be placed. Case cushions are particularly useful in supporting the watch when it is under a press.

The diameter of a round wristwatch case. The case diameter refers to the distance of one extremity of the case flank to the other, excluding protrusions such as lugs, pushers, crown guards, etc. It is the most commonly used metric for measuring watch size, though it can be deceiving due to other measurements such as dial diameter and lug-to-lug. Case diameter is not used for shaped cases.

Also called the 'side case' or 'case side'. The side profile of the case of a watch.

A bladed tool that is designed to open snap-on casebacks. The blade is usually blunt and made of a soft metal or plastic as to avoid damaging the case.

The geometric shape of a case, referring to only the main case and not the lugs unless they are integrated into the design. In the rare instances where the dial shape does not match the case shape (e.g. round case with a rhombus dial or a square case with a round dial), the two should not be confused. Case shapes are largely divided into round cases and shaped cases, the latter referring to any case that is not circular.

The aesthetic style of a case, typically referring to the case in its entirety including the lugs and sometimes the caseback. Case styles are often named after famous and influential designs. Some examples include the Calatrava (Patek Philippe), Oyster (Rolex), Clamshell (Gallet), and Tank (Cartier) cases. Sometimes case styles are named after famous casemakers such as Spillmann, Borgel, and Hagmann. They may also be named after certain defining features such as stepped case (case with a stepped bezel), tre tacche (caseback with three notches, usually also with a stepped bezel), and savonnette (pocket watch with front cover).

A caseback opener in the form of a clawed wrench designed to open screw-down casebacks. The wrench usually has three teeth that can be adjusted with screws. The teeth made be made of hardened plastic or metal. While wrenches are the best way to open tight screw-down casebacks, poor contact with the notches or grooves in the caseback frequently result in gashes and scars.

The backside of a case. The caseback is usually a removable lid which allows access to the movement for basic repairs. In so-called 'monobloc cases' the caseback is not a separate component but rather simply the backside of the case.

A tool that is designed to open casebacks. Due to the wide variety of caseback types, there are different openers for each style. Snap-on casebacks are usually opened with a knife. Screw-down and bayonet casebacks are typically opened with a wrench, friction ball, or a dedicated tool. Screw-in casebacks are opened with a screwdriver.

A press that is designed to open and close casebacks. The presses can come in various forms fitted to different types of caseback. Caseback presses are particularly useful for safely opening and closing screw-down casebacks as they provide a stable purchase on the watch and the rotating opener, minimizing the risk of slipping and scratching the caseback.

An individual or production facility that specializes in the fabrication of cases.

A mark that symbolizes an individual casemaker or casemaker company. Not all watches have a casemaker's mark but they can often be found on the inner surface of the caseback. Some guilds have a numerical system which designates a unique number to each registered casemaker.

A watch manufacturer established in Tokyo, Japan in 1946. Casio is owned by the Casio Group.

A nickname for the Casio AE1200 series worldtimers. The origin of the nickname is likely the 1967 James Bond film Casino Royale, but the watch did not exist then nor did James Bond ever wear a Casio. It is likely a reference to the watch’s similarity to the Seiko G757 Sports worn by Roger Moore in the 1983 James Bond film Octopussy.

A nickname for the Casio G-SHOCK 2100 series watches. It is a tongue-in-cheek name that pokes fun at the watches' resemblance to the Audemars Piguet Royal Oak. Also see 'Royal Broke'.

(Italian) Coin case. A style of case that has a flat, slab-sided bezel resembling a coin and typically a slab-sided case as well. The name originates from Longines catalogs. The term is often erroneously translated to ‘coin edge case’ in the Anglosphere. Also see ‘coin edge (misnomer)’.

A metalworking technique that involves the pouring of molten metal into the cavity of a mold. Casting is an extremely uncommon method in watchmaking because it is time-consuming and not intricate enough. In some limited instances, lost-wax casting or investment casting is used to produce cases. See ‘lost-wax casting’.

Watch collecting parlance for selling a watch not long after purchase because of buyer’s remorse. Not to be confused with ‘flipping’, which is the act of selling a watch immediately after purchase for profit.

A style of hands distinguished by broad surfaces usually filled with copious amounts of lume that is divided into sections which make the hands resemble stained glass windows on cathedrals. The walls between the lume pools also resemble the veins of a leaf. A cathedral hour hand is usually spade-shaped and feature elaborate veins. The minute hand is plume-shaped and feature simple, horizontal divisions. The seconds hand is normally tip with a diamond-shaped lume plot but may not be lumed at all. Cathedral hands were among the first style of lumed hands and were thus frequently used in military watches. They are still a common sight on vintage-inspired watches today. Cathedral hands are typically lumed.

The link that is at the center of a bracelet.

A type of seconds hand which is mounted on the center stack and whose range of movement occupies the entire area of the dial. Center seconds offer superior legibility and are particularly crucial for watches focused on high accuracy or intended for some form of measurement. Some experts consider it a complication as the natural position of the seconds hand follows the location of the fourth wheel, which is mounted off-center. This requires an addition of a gear train to 'move' the seconds hand to the center of the watch. However, this is no longer common due to fundamental changes in wheel train arrangement. See 'indirect center seconds' and 'direct center seconds'.

The handstack at the center of a clock. Clocks that do not have the traditional concentric layout (such as regulators) do not have center stacks.

The wheel of the going train located at the center of the movement and dial. In a typical movement the second wheel serves as the center wheel. However, for certain movements the fourth wheel is moved to the center. Some movements may not have a wheel at the center at all.

The arbor that lies at the center of a typical mechanical movement, primarily mounting the second wheel (center wheel). The arbor also mounts the important cannon pinion, and by extension the minute hand, hour wheel, and hour hand. In certain designs, it would also mount the fourth wheel and seconds hand by extension.

A chronograph whose chronograph hands are mounted to the center stack instead of inside sub-registers. This configuration is standard for the chronograph seconds hand because a centrally-mounted hand is far easier to read. However, some chronographs feature centrally-mounted chronograph minute hands as well. The tradeoff for superior legibility is the potential for confusing the chronograph hands with the regular hands.

A type of oscillating mass in an automatic mechanical movement that is mounted on the center of the movement and utilizes the entire circumference of the movement as its travel distance. The central rotor is by far the most common type of oscillating mass. A central rotor is simple and efficient but adds height to the movement as it requires an extra layer.

A governor for a striking train which employs a spindle with two weighted arms to regulate the strike tempo. The extent to which the arms are allowed to move when the spindle is in motion determines the speed of the striking train. This distance can be adjusted to make the repeater train go faster or slower.

A nickname for the Rolex Oyster Perpetual Submariner reference 126610LV, a Submariner with a green Cerachrom bezel and black dial. The name is a portmanteau of 'ceramic' and 'Kermit', the latter being the first Submariner to have a green bezel. This reference is also called the 'Starbucks' due to its having a noticeably different shade of green from the lime green of the Kermit. However, the updated color on the 126610LV starting from 2023 (the 70th anniversary of the Submariner and 20th anniversary of the Kermit) has started a differentiation between the more hunter green Starbucks and the more lime green Cermit. The updated 126610LV now sports a green that is much closer to the original Kermit, the only major cosmetic difference being the use of a ceramic bezel insert instead of an aluminum one.

A nickname for the first variant of the Rolex Oyster Perpetual Milgauss reference 1019 which features a non-lumed dial believed to be ordered by the European Organization for Nuclear Research, or CERN (Centre Européen de Recherche Nucléaire). The non-luminous dial was requested because the tritium lume would interfere with radioactivity readings. While the Milgauss was indeed developed at the request of CERN, the story behind the first generation dial is not completely confirmed.

A document certifying the authenticity of a watch in part or in whole. A certificate can be issued on request of an individual from the manufacturer as most watches do not come from the factory with such a certificate (it is redundant with the original documentation which serves as a proof of authenticity anyway). A certificate of authenticity can be a suitable replacement for a lost original document containing the watch’s serial number(s). Manufacturers who do issue these certificates require the watch to be physically submitted to their facility for inspection. Alternatively, some third-party organizations and jewelers may certify the authenticity of a watch with varying levels of reliability. It should be noted that not all manufacturers provide this service and that even those who do may not accept vintage watches. Certain retailers and jewelers who carry the brand may offer this service independent of the manufacturer.

Spelled ‘cesium’ in American English and ‘caesium’ in British English. An element used in the timekeeping organ of an atomic clock. Its single stable isotope, cesium-133, is the key element of an atomic clock and is used in the SI definition of a second.

A nickname for the Seiko 6139-600X series automatic chronographs with blue dials. These watches are also called ‘Blue Pogues’ as ‘Pogue’ is the most widely accepted name for the entire 6139-600X series. The name ‘Cevert’ is an homage to François Cevert, a French Formula One racing driver who wore the blue-dialed 6139-6009.

(French) An unassembled movement. ‘Chablon’ normally means ‘stencil’.

(French) A maker of fine chains, especially for pocket watches.

A method of finishing where a right-angled corner is ground to a 45 degree bevel and highly polished. Also known by the French term ‘anglage’. Also see ‘beveling’.

(French) A decorative technique where vitreous enamel is poured into carved or cast recesses on a surface. It produces a similar effect to cloisonné, albeit with an opposite technique - in cloisonné the surface is merely lined with metal to provide compartments for the different colors whereas in champlevé the colors are poured into recesses cut into the metal. Usually the immediate giveaway is that cloisonné has more visible colors interspersed by metal linework while champlevé is mostly metal with portions of color. This is not always accurate, however. Moreover champlevé is a strictly enamel technique whereas cloisonné is a broader term that includes coloring with gemstones and pieces of solid glass.

The ring of hashes, indices, markers, or other indications that are graduated to show the minutes and seconds. Synonymous with 'minute track'. In Rolex parlance, a chapter ring is a minute track whose hashes are all connected to an outer ring. Meanwhile in Seiko parlance, the chapter ring is very often confused with the 'rehaut', which is the wall surrounding the dial of a watch. This may be because chapter rings in Seiko dive watches are often mounted on rehauts. It should be noted that both Rolex and Seiko-specific understandings of the word are incongruous with its actual definition.

Military timezone name for UTC-3.

(French) Short for ‘cheville de plateau’, ‘plateau’ being the French term for the roller. See ‘impulse jewel’.

A dial configuration of the Rolex Oyster that is divided into quadrants with diagonal hatching towards the center of the dial. The hatching resembles a stack of chevrons, hence the name.

A series of strikes, sometimes arranged into a melody.

A day wheel with the days of the week written in Chinese. As most Chinese languages count days using numbers, the days are numbered (in Chinese characters) 1 to 6 for Monday to Saturday and the character for 'sun' for Sunday. Some non-speakers confuse the Chinese day wheel with the more famous Kanji day wheel. While both are written in Chinese characters, the day systems are completely different save for the character for Sunday.

Chocolat, Noir. Rolex nomenclature for a brown and black bi-color bezel.

A watch and jewelry manufacturer established in Sonvilier, Switzerland in 1860 and currently headquartered in Geneva, Switzerland. Chopard is privately owned.

A stopwatch. A chronograph is a mechanical complication that records elapsed time. In modern usage any watch with a stopwatch function can be called a chronograph. Not to be confused with 'chronometer', which is a term for a precise timepiece.

A component of a chronograph mechanism which is a bridge, usually shaped like a Y, which mounts the chronograph runner and minute recording wheel. Some watches have separate bridges for the two wheels. The chrono bridge typically occupies the center of the movement and sits right above the balance. It is one of the key defining visual features of a chronograph movement.

A component of a chronograph mechanism which operates the chronograph seconds hand. The chronograph runner derives its energy and rotation speed from the coupling wheel, which in turn is controlled by the driving wheel, which in turn is controlled by the fourth wheel. The runner has a sixty-second finger which initiates the minute recording wheel to move once every minute. The chronograph runner can be easily identified as it occupies the center of the movement and is mounted on the prominent chronograph bridge.

A precise timepiece. A chronometer is any timepiece that is very accurate according to a set of standards. Most timepieces are awarded chronometer status by various third party testing organizations such as COSC. Not to be confused with 'chronograph', which is a timing complication akin to a stopwatch. See also 'marine chronometer' and 'observatory chronometer'.

The science of timekeeping and its standards. In the past, the term 'horology' was used to this effect but has since changed to refer to the study of timekeeping devices, many of which are considered obsolete by modern institutional timekeeping standards.

(Italian) Big chocolate. In the Italian watch collecting community, ‘cioccolatone’ is a nickname given to square or stout rectangular watches for their resemblance to big pieces of chocolate. In the Anglosphere, the name is mostly associated with the Vacheron Constantin reference 4737 which features a carré galbé (curved square) case.

A watch manufacturer established in Tokyo, Japan in 1918. Citizen is owned by the Citizen Group.

Statutory time commonly used and understood by civil society. Civil time is usually set by national institutions as a positive or negative offset of UTC (Coordinated Universal Time). Civil time may be different from time standards used by certain industries or professions such as navigation, geodesy, engineering, astronomy, and physics.

A component of a watch band that opens and closes to enlarge and tighten the band. The clasp is one of the two major locking mechanisms for a band alongside the buckle. A clasp is distinguished by its use of locking and releasing metal parts as apposed to a buckle where the pin/tang fastens to a simple hole. The vast majority of clasps also perpetually connect the two ends of the band unlike a buckle where the two ends are separated when not on the wrist. Some advantages of the clasp are its sturdiness, ability to reduce wear on a strap, and lower risk of dropping the watch when putting it on. Disadvantage include comfort, weight, price, and inability to lay the watch flat on a surface without removing the clasp. Naturally, all bracelets are only compatible with clasps with the exception of a few strap-style bracelets that may use a tang buckle or sliding buckle. Also see 'buckle'.

A style of indices/markers in the form of a long triangle with a fluted surface on the outer half and a smooth, faceted surface on the inner half that resemble an animal claw or talon. The name is most associated with Rolex watches, namely certain Day-Dates in the 1960s.

Synonymous with 'water clock'.

A movable lever that engages a moving component to allow motion in only one direction and prevent it in the other. In industrial parlance, 'pawl' is the more commonly used synonym. In watchmaking, 'click' is more common. Clicks can be spring-loaded at the pivot. They can also be pressed down by a flat spring called a click spring. In some cases, the end of a click spring acts like a click. Together with the ratchet wheel, the click forms the ratchet mechanism.

A rotating bezel that has a clicking action with tangible steps or clicks. Click bezels are fitted on top of a click spring, a circular wire spring with at least one curved end that engages with the tooth-lined interior wall of the bezel. The click spring's purpose is to provide resistance to the action so that it advances in clicks. Depending on the shape of the spring a click bezel can be engineered to be unidirectional or bidirectional. Also see 'friction bezel'.

A spring which maintains pressure on the click or acts as a click, usually in a ratchet assembly. When used in conjunction with a pawl or click, it maintains pressure on the click so that it seats properly at root of a gear tooth. This is common for the barrel assembly. When used as a click (usually with an annular/internal gear), a click spring is bent against the desired direction so that a tooth turning in that direction will simply push the bent end down. If it attempts to move the other way it will have the end of the spring stuck in its root. This is useful in unidirectional rotating bezels. Sometimes click springs are used for other purposes. In many bidirectional bezels, the click spring is bent so that the teeth on the inner gear can move when sufficient force is applied. This allows the bezel to stop precisely where it needs to, prevents it from wobbling or moving too much, and provides satisfying tactile and auditory feedback.

A device that measures and/or indicates time. Synonymous with 'timepiece'.

The mechanics of a clock or similar devices. Usually refers to mechanical devices. The term is more general than 'movement' and can include the assembly of gears, springs, levers, and/or weights used to power non-timekeeping objects like music boxes or wind-up toys.

(French) A decorative technique where colored material is outlined with (usually precious) metal. While cloisonné may incorporate any colored material including gemstones, paint, and glass, in watchmaking the term is generally associated with vitreous enamel. Cloisonné is most commonly seen on dials and uses colored vitreous enamel and gold wire. The term comes from the French word 'cloison' (partition) which refers to the metal linework which demarcates the compartments of colored material. Also see 'champlevé' for a similar technique.

A counterfeit watch. Typically, a clone refers to a ‘replica’ of higher quality.

(French) Paris nails. See ‘hobnail’.

A gear with asymmetrically-profiled teeth which slope in one direction and peak at a hook. Club-tooth gears usually serve as escape wheels in Swiss lever escapements.

A mechanism that allows the rotating input shaft to disconnect from the output shaft, or vice versa. In watchmaking, clutches are primarily used in chronographs and can either be horizontal or vertical. They are also sometimes used in winding mechanisms to prevent overwinding.

An escapement that utilizes two co-axial balance wheels with an ultimate goal of increasing precision and longevity by reducing friction. The co-axial escapement utilizes two balance wheels to engage four pallet jewels, dividing the roles of impulse action and locking action to one pair of pallets each. Several factors lead to reduction of friction. First, as one of the pallets is located directly on the roller, the impulse delivery is more direct. Second, the division of roles means that a pallet jewel does not need to advance the tooth of the escape wheel via sliding against it. Previously this was because the jewel also needed to be shaped to lock the tooth. This allows the pallet to push directly on the tooth, reducing a great deal of sliding friction. Third, the reduced friction reduces the need for lubrication, which may have an adverse effect on accuracy in the long run.

A watch is co-branded when it carries the emblem or name of a company other than the manufacturer of the watch and/or its components. Co-branding is slightly different from double-signing which is limited to retailers and jewelers who add their own logos to watches they sell. Co-branding is far broader and can include watches that are made in collaboration with or for corporations, government agencies, and trademarks. For example, the famous Rolex Oyster Perpetual watches with the Domino’s Pizza logo on the dial are co-branded, but not double-signed.

A structural piece of a movement that is fastened to the plate on one end. The other end usually mounts a wheel of some sort. Cocks are space-efficient as they are shorter than bridges which are fastened at both ends. However, they are generally not as good for shock absorption. The most famous cock is the balance cock, which suspends the balance assembly. Also see ‘bridge’.

A category of wristwatch designed for high society ladies to complement their formal evening dress, particularly in the 1920s. Cocktail watches are distinguished by their diminutive size, elaborate diamond-studded case, and thin satin strap or bracelet. They almost invariably came as two-handers as the size was too small to accommodate even a seconds hand.

An edge with ridges, reeds, or grooves that resemble those of a coin. Coin edges are commonly used in rotating bezels to improve grip. Not to be confused with ‘coin edge case’, an erroneous name for a type of case. See ‘coin edge (misnomer)’.

In vintage watch collecting, ‘coin edge’ is a misnomer to describe watches with a flat bezel. The term likely originates from a poor translation of ‘cassa a moneta’, an Italian term meaning ‘coin case’ that referred to the flatness and thinness of the flat bezel. The term is mostly used in association with vintage Longines watches.

A nickname for a bi-color bezel consisting of black and red. It is most famous as the nickname for the Rolex Oyster Perpetual GMT-Master II reference 16760, a GMT-Master II with a black and red aluminum bezel and red GMT hand. The watch was also dubbed the 'Sophia Loren' and 'Fat Lady' for its large case.

A ring to which the inner end of the balance spring is pinned. The collet connects the balance spring to the balance staff.

A chronograph which utilizes a column wheel as its control system. Column wheel chronographs are reputed to provide a smoother and satisfying pusher feel and are seen as more refined and beautiful due to the aesthetic design of the column wheel and the various levers and hooks that engage with it. Column wheel chronographs have more complex mechanics and thus have tighter tolerances. However, with modern manufacturing technology, the reliability of the average column wheel chronograph has improved significantly and can be found on higher-end chronographs. Also see ‘cam chronograph’ for comparison.

A component of a chronograph mechanism in the form of a hook/beak/click which snags the ratchet teeth of the column wheel and advances it forward. The hook is connected to the column wheel lever by a pivot.

A component of a chronograph mechanism which applies constant pressure to the column wheel so that the wheel turns in the desired manner and is stationary otherwise.

A chronograph control system which takes the form of a ratchet wheel with an extra ring of raised trapezoidal teeth that resemble battlements. The ratchet teeth engage with the operating lever click/column wheel hook which advances the column wheel clockwise. The column wheel moves one click every time the chronograph is started or stopped. The castellated column teeth engage with fingers of various levers. Upon the push of the start/stop pusher, the column wheel moves a click and pushes the finger of the chrono wheel brake which frees the chrono runner while simultaneously allowing the finger of the coupling lever to fall between the column teeth and pivoting the coupling lever so that the coupling wheel attached to it connects the driving wheel and chrono runner. Stopping is simply the reverse. The column wheel also blocks the reset lever from moving when the chronograph is running. When the chronograph is stopped, the column wheel allows the reset lever to move through the space between its columns.

An instrument that points to magnetic north and the three other cardinal directions. Compasses are used to determine orientation and bearings in navigation.

‘Compax’ is a confusing and often misused term. The term can refer to a specific chronograph made by Universal Genève and the subsequent series of chronographs that came after it (see ‘Compax (Universal Genève), watches that use UG Compax movements, watches that look like a UG Compax, or a numbering system for sub-registers on watches. The last use is technically incorrect, as the Compax numbering system was [number of sub-registers - 1] because it counted complications, not sub-dials (one sub-dial was always for the running seconds). Nonetheless, it is now popular to call chronograph dial configurations bi-compax, tri-compax, or quadri-compax depending on its sub-dial count.

A branded term for a wristwatch that has one or more complications, starting from a chronograph. The term was coined by Universal Genève and adopted by the many companies that purchased UG movements. Thus Compax is used mostly for UG watches or watches that use UG movements. The original Compax was a triple-register chronograph. After this, UG started adding number prefixes, which show how many complications there are. For example, a Uni-Compax has one complication: the chronograph. UG never made a Bi-Compax but did make a Tri-Compax with a chronograph, moonphase, and calendar. Also see ‘compax (general)’.

See ‘bimetallic balance wheel’. Also known as a ‘self-compensating balance’ or ‘compensation balance’.

See ‘bimetallic balance wheel’. Also known as a ‘self-compensating balance’ or ‘compensating balance’.

A simple calendar complication that displays the date, day, month, and moon phase. It is a triple calendar with a moon phase complication. However, the distinction between a triple and complete calendar is hazy and many use the two terms interchangeably. The complete/full calendar is sometimes confused with the perpetual calendar due to their visual similarities. The major difference is in the mechanics and the existence of a leap year indicator.

In watchmaking, a complication is any mechanical feature of a timepiece that performs a function beyond the display of hours, minutes, and seconds. Typically, for a feature to be recognized as a complication it must have two attributes: one, it must be mechanical and not activated by electronics and two, it must be mechanically integrated within the movement. Therefore, features on a quartz watch are not generally regarded as complications. Neither are features such as a rotating timing bezel, compass, humidity indicator, or thermometers. Nonetheless, there is still great debate on what mechanical features can be considered complications. Complications can be divided into many families depending on their purpose, even though there is no consensus on the precise taxonomy.

A subcategory of dive watch that utilizes the special compressor or super compressor case, or a watch that mimics the style of such a watch. The latter is more accurately called a 'compressor-style diver'. Compressor divers typically feature two crowns, one for the usual crown functions and an extra to operate the rotating internal bezel. While there is no rule that compressors must be dual-crowned and have an inner bezel, these patented cases were delivered to their clients that way and have thus become a part of the compressor look.

A type of dive watch case whose caseback is sealed increasingly tighter by water pressure. Compressor cases use spring-loaded casebacks that only become as watertight as they need to be. They feature snap-on casebacks which were almost immediately followed up with screw-down casebacks in the newer super compressors. Also see ‘super compressor case’ and 'compressor'.

A style of hands distinguished by their ability to contract and expand depending on their position in order to reach the markers of an oval dial. The hands are essentially scissors mechanisms with multiple articulating joints that are manipulated by oval cams on the center stack. This allows the hands to contract when passing through the minor axis areas and expand when passing through the major axis areas. The name comes from how the scissors mechanism resembles the bellows of a concertina or accordion. Concertina hands are incredibly rare.

A style of crown distinguished by deep fluting and a conical profile culminating to a flat or slightly bulbous top. Conical crowns are usually oversized and easy to grip as they were designed for aviators who were operating the crown with gloved hands. Therefore conical crowns are a common feature of pilot's watches. Often confused with the similar 'onion crown', which looks similar and serves the same purpose.

A nickname for the Omega Constellation.

A mechanism which evens out the variable force released by the unwinding of the mainspring. The force and torque of the mainspring influences the beat rate of the watch which ultimately affects its accuracy. A constant force mechanism acts as a mediary between the mainspring and escapement. This can be achieved in many ways including an extra intermediary escapement, fusée-and-chain, or an extra spiral torsion spring called a remontoire.

In pocket watch collecting nomenclature, a convertible dial is a dial that ‘converts’ a savonette pocket watch (a watch with its crown at 3 o’clock) into an open face/Lépine pocket watch (a watch with its crown at 12 o’clock). In essence it’s a dial that is mounted 90 degrees to the right, thus sporting the seconds hand in the very unconventional 3 o’clock position instead of the usual 6 o’clock position. A watch with a convertible dial was often called a ‘sidewheeler’. Also see ‘convertible movement’.

In pocket watch collecting nomenclature, a convertible movement is a watch movement designed with an easily modifiable winding stem position so that it can be converted to either a savonette pocket watch (a watch with its crown at 3 o’clock) into an open face/Lépine pocket watch (a watch with its crown at 12 o’clock). Also see ‘convertible dial’.

An element very often used in the manufacture of watches. Copper is one of the most important materials in watchmaking, especially as a part of an alloy. It is combined with zinc to produce brass, which is used ubiquitously for the crafting of plates and bridges. When combined with beryllium it makes up balance wheels and springs. Combined with tin it becomes bronze, a niche but well-known material for constructing dive watch cases. Copper is an essential ingredient in virtually all types of colored golds, including yellow, red, pink, rose, and even white gold. On its own it serves as the balance of many alloys that dials are made of.

A galvanized gilt dial that uses a copper or copper-colored substrate, or a dial that has a similar appearance.

A dial made of the gemstone coral.

(French) Cow Horns. A style of lugs that resembles cow horns. Also the name of a Vacheron Constantin chronograph with these lugs.

In watch collecting parlance, a component of a timepiece is said to be ‘correct’ when it is the correct component that belongs on the timepiece but not necessarily original to the timepiece itself. The scope of correctness may vary. To say that a component is ‘period-correct’ is to say that the component belongs to the period of manufacture (e.g. a 1930s handset on a 1930s watch) but not necessarily that it is correct to the exact model (e.g. the aforementioned watch may never have been offered with that handset) or that it is original to the watch (e.g. the handset may be correct in every way but not the original hands installed from the factory). Used most frequently when discussing the components of vintage watches and assessing their authenticity.

A mechanical actuator flush to the case which is actuated by being pushed. A corrector is usually in a small round dimple on the case flank. While it can only be actuated with a corrector tool (a small pen-shaped tool with a pin), it has the advantage of being unnoticeable from the front and giving the watch a smoother profile than a protruding pusher. Therefore it is typically used for complications that do not need constant interaction such as dates, calendars, and moon phases.

A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1955. Corum is owned by the Citychamp Group.

(French) Contrôle officiel suisse des Chronomètres. ‘Official Swiss Chronometer Testing Institute’. A Swiss organization that certifies the accuracy and precision of watches. In English it is pronounced either [kosk] or read letter-by-letter. COSC-certified watches are said to meet the ‘COSC standard’.

A mechanical or quartz watch that is certified for accuracy by the Official Swiss Chronometer Testing Institute or COSC.

A set of standards for watch accuracy set by the Official Swiss Chronometer Testing Institute or COSC. COSC maintains different standards for mechanical and quartz watches. Both typically test the watch for around two weeks (13 days for quartz, 15 for mechanical) and check average daily rate of deviation from an atomic time standard, as well as variation in daily rates, accuracy in different positions, and effects of temperature. A watch certified by the COSC standard is called a ‘COSC chronometer’.

(French) Geneva stripes.

A rotating bezel with count-up markings.

A rotating bezel with countdown markings.

A nickname for the Seiko reference 5718-8000 chronograph. The nickname is a matter-of-fact description of the watch's complications: a digital lap counter and chronograph.

An unauthorized copy of an authentic clock, usually a watch.

A component of a chronograph mechanism which constantly applies pressure to the coupling arm/lever. This constant pressure which pushes the arm towards the center of the watch where the chrono runner is allows the coupling arm and its wheel to slide towards the chrono runner and start the chronograph. Also called the ‘pivoted detent spring’.

A component of a chronograph mechanism which moves the coupling clutch wheel bridge and thus is responsible for connecting and disconnecting the driving wheel which provides the energy and the chronograph runner/chronograph wheel which controls the chronograph seconds hand. Mechanically it is equally an arm, a lever, and a clutch, so the three terms may be used interchangeably. As it is also a pivoted detent (referring to its shape as a pivoted lever and its finger which serves as a detent), the arm is also called a ‘chronograph pivoted detent’.

A component of a chronograph mechanism which transfers energy from the driving wheel to the chronograph runner. The coupling wheel is mounted on a pivoting bridge which allows it to make contact (engage) and break contact (disengage) with the chronograph runner.

A component of a chronograph mechanism which mounts the coupling wheel and is controlled by the coupling clutch. It is screwed onto the coupling clutch and is often simply regarded as a part of it instead of its own component. As it is mounted onto a pivoted detent (referring to its shape as a pivoted lever and its finger which serves as a detent), it is also called a pivoted detent bridge.

A plate that mounts the intermediate wheel and moves into position to mesh it with the minute wheel. The cover plate is machined with an integrated detent spring which rests on a pin on the setting lever. When the crown stem is pulled into setting position, the setting lever moves, pushing the detent spring and the rest of the cover plate so that the mounted intermediate wheel can mesh with the minute wheel.

Collection Privée Cartier Paris. A range of timepieces made by Cartier in 1998 in response to a renewed demand for mechanical timepieces. CPCP watches revived many designs from Cartier’s past and used mechanical calibers instead of quartz modules. The CPCP lasted for about a decade and came to an end in the late 2000s.

A style of lugs with an inward curve that resemble crab claws. Also known as ‘crab claw lugs’. Crab lugs are somewhat ill-defined, and spider, teardrop, and horn lugs are often conflated with crab lugs. Generally, crab lugs have a noticeably curved profile unlike the angular profile of spider lugs. Each lug resembles the propodus (the fixed, larger, and curved part) of a crab or lobster’s pincer.

A brand of high horology watches owned by Seiko.

A type of engagement failure that occurs when the threadings of the male and female components do not align correctly, typically as a result of incorrect angle of insertion or excessive force. Cross-threading may lead to stripping.

A dial style with a crosshair at its center. The crosshair divides the dial into four quadrants, which is supposed to make the dial more legible. It is also a stylistic choice. Many subdials also utilize the crosshair design. In some instances, the crosshair dial is regarded as a type of sector dial. In the strictest sense, a crosshair dial is divided into quadrants while a sector dial is divided into rings. However, the two are not mutually exclusive and are often combined.

See 'broad arrow'.

A button-shaped knob with a knurled, fluted, or otherwise textured rim that allows the wearer of a clock to interact with the movement without opening the case. The crown is primarily used for setting the time, winding the mainspring, and setting other features in the clock. A crown can be pulled out to various positions to access its different functions.

A removable cap that goes over the crown to bolster its water resistance or protect it from knocks. Most styles of crown caps are a variation of the canteen crown.

A gear with teeth, often saw-teeth, arranged in a ring at a right angle to the face of the wheel and parallel to the axis of rotation. It resembles an archetypal crown. It is similar to the bevel gear, of which it may be considered a type, but the key difference is that a crown gear's pitch cone angle is 90 degrees whereas any other pitch cone angle would make the gear a bevel gear. They are visually very distinct from each other. Moreover, unlike bevel gears which typically mesh with other bevel gears, crown gears usually interact with spur gears or even rods. Crown gears were hugely important in watchmaking during the days of the verge/crown wheel escapement. Today, crown gears are even more ubiquitous as they are essential components of the crown stem assembly which transmits power from the winding stem (a rod) to the wheel train.

A protrusion from the case which flanks the crown to protect it from external impact. Crown guards usually come in pairs. While the reduction of exposed crown area makes it slightly more difficult to operate the crown, the payoff is that the most vulnerable part of the watch is protected from at least three sides: the rear where the wrist is, and the top and bottom. Crown guards are common on dive watches.

A stem that is connects the crown and the keyless works of the watch. The crown stem’s primary roles are to wind the mainspring via the winding pinion and set the time via the sliding pinion. Thus, a typical crown stem consists of a threading at one end for the crown, a winding pinion a little further down from the midsection, and a sliding pinion at the other end.

A component of the keyless works that connects the crown stem’s winding pinion and the ratchet wheel that sits on the mainspring barrel. The crown wheel can be easily spotted as the smaller toothed wheel that sits next to the ratchet wheel.

A type of wheel where the leaves/teeth are parallel to the axis of rotation, as opposed to perpendicular like in most conventional gears. This gives the wheel the appearance of a crown, hence the name. The crown wheel is a crucial component for the crown wheel or verge escapement. It should not be confused with a component of the same name, whose name comes from its relationship with the crown of a watch.

See 'verge escapement'.

The transparent material at the frontside of a clock which allows the viewer to read the information on the dial while simultaneously protecting it from the outside. Crystals are usually made of some form of plexiglas, mineral glass, or sapphire.

An electronic oscillator circuit that uses a piezoelectric crystal as a frequency selective surface. In watchmaking, the oscillator's property as a frequency selective surface allows it to serve as a timekeeping device. Many types of crystals can be used to make these oscillators, but the quartz crystal is by far the most common in watchmaking. The crystal oscillator is the key component of a quartz movement.

A tool that is designed to press a crystal into a watch case. The press looks like a typical mechanical press with a lever handle and a spring-loaded pressing cylinder with a plastic or hardened rubber pressing surface.

A pin that holds onto the balance spring and determines its free/effective length. Curb pins usually come in pairs.

A piece of watch furniture meant to have a watch strapped around it. Usually made of velvet, silk, satin, or other soft fabrics and sometimes stuffed with plushy material. Some cushions are hard and non-pliable in order to give structure. Similar to a pillow.

A case shape that is either a square with four convex sides or a round case with an unbroken semicircular line running from the tips of the lugs to the case flank. The first style can be understood as the inverse of a carré galbée case. The second style is basically a round case with beefier round contours on the case flanks. As the two styles are very different despite having the same name, the latter is often also called a turtle case after the famous Seiko Turtle diver.

A style of integrated lugs that comes on a cushion case (second variety in the ‘cushion case’ entry).

The inner cover behind the hinged cover of a pocket watch. In pocket watches the cuvette typically contains information on the watch's movement or technical specifications. In a looser sense 'cuvette' is used to describe any sort of solid metal hinged cover.

A gear tooth profile based on a cycloid as opposed to an involute. A cycloid is a curve generated by rolling a circle across a line. A cycloid tooth profile takes its shape from sections of a hypocycloid and epicycloid, the former being a curve formed by rolling a circle along the inside of a larger circle and the latter being a curve formed by rolling it on the outside. The dedendum of the profile is hypocycloidal while the addendum is epicycloidal. In simple terms, a cycloid tooth looks like a rectangle with a pointy end and can be distinguished by its relatively straight flanks. This is in contrast with the curvy involute tooth. Today, cycloid profile teeth are almost entirely associated with watchmaking as the rest of the world has moved on to involute profiles. Cycloid teeth retain the upper hand as they provide maximum durability, longevity, minimal friction and wear when there is i) no direct lube, ii) tight space, and iii) long maintenance intervals.

Synonymous with 'magnifier'. A term famously used by Rolex.

A style of indices/markers in the form of a long, thin isosceles triangle, typically faceted like an archetypal dagger blade.

See ‘beater watch’.

See 'damaskeening'.

Also spelled 'damascening'. A finishing technique on the movement where radial and/or circular geometric patterns are etched using a rose engine or similar device. It is similar in many ways with 'guilloché', the difference being that the patterns in damaskeened watches are much shallower, often being simply ground and not carved. Whereas guilloché is almost always a radial pattern, damaskeened embellishments are at times whimsical. The term 'damaskeening' originates from the Syrian city of Damascus and their namesake steel famous for its marbled pattern. The term is almost exclusive to American pocket watches.

A watch manufacturer established in Barbing, Germany in 1994. Damasko is privately owned.

A nickname for Heuer Monaco reference 74033N, a blacked-out Monaco with a matte PVD case, black dial, and orange accents.

A nickname for Universal Genève Compax reference 885103/1 ‘Nina Rindt’ chronograph with a reverse panda dial.

Another name for the finger of the chronograph runner.

A nickname for the Seiko SBBN011 diver and any other Tuna that is all-black. 'Darth' is a common prefix attached to watches that are predominantly black. It originates from Star Wars lore.

A nickname for the Omega Seamaster reference 145.0023, a black tungsten version of the reference 145.023 nicknamed the ‘Anakin Skywalker’. The nickname ‘Darth Vader’ is a reference to the black helmet-shaped shell and was dubbed by renowned collector Chuck Maddox alongside the Anakin Skywalker. In Star Wars lore, Darth Vader is the name of Anakin Skywalker after he turned to the Dark Side much like how the ref.145.0023 and the ref.145.023 are essentially the same watch but in opposite colors.

A pusher on a watch that adjusts the date display.

A style of hands distinguished by a bold triangular profile. Unlike most hour and minute hands the shoulder (widest point) of a dauphine hand is at the mounting point. The hand culminates with radical triangular taper at the tail. The etymology of ‘dauphine’ is uncertain. A dauphine is the crown princess of France and wife to the dauphin. A dauphin is either the crown prince of France or French for dolphin, the former being derivative of the latter. It is possible that dauphine was a misspelling of dauphin as there is a theory that the name comes from how the sleekness of the hands resembles that of a dolphin. Dauphine hands may be lumed or unlumed.

A watch manufacturer established in Sainte-Croix, Switzerland in 2002. De Bethune is privately owned.

A variation of the anchor escapement that eliminates its inherent recoil, hence the name 'deadbeat'. Also called the 'Graham escapement' after a clockmaker erroneously believed to be its inventor. The deadbeat escapement addresses recoil by switching the slope direction of the escape wheel teeth. The deadbeat teeth are pointed towards the direction of rotation while the anchor teeth point against it. The teeth face engages with the pallet face and locks instead of recoiling, completely stopping the escape wheel until it is released on one end and pushed with the other pallet. While more accurate than the base anchor escapements, deadbeat escapements were limited by their tighter manufacturing tolerances. Hence they were used for higher grade clocks.

A complication that advances the seconds hand once every second instead of multiple times per second. This is achieved through a secondary escapement which releases the seconds hand only once per second instead of allowing it to move at its natural rate as dictated by the balance. Deadbeat seconds is a useful complication for observation and measurement purposes as it makes the distinction between each second much clearer than a movement which moves multiple times per second. With the advent of quartz watches that naturally tick once per second due to their stepping motor, mechanical watches with deadbeat seconds are sometimes mistaken for quartz watches. Nonetheless, the complication is still appreciated within horological circles.

A subcategory of dive watch that is designed for ultra-deep depths. Typically watches rated to beyond 1000m of water resistance may be called deep divers. In a sense there is no meaningful difference between deep divers and professional divers other than water resistance. However, the deepest-rated divers often boast oversized, often unwearable cases. These are usually technology demonstrators and not meant to be worn by humans but rather strapped to the robot arms of an ultra-deep submersible.

Military timezone name for UTC-4.

A single or double-fold clasp. Commonly referred to as a 'deployment' clasp, which is an English translation of the French word 'déployant'. While all folding clasps are also technically deployant clasps, the term usually refers to those on straps, not bracelets. This is because bracelets rarely use anything but folding clasps as a locking mechanism (and are thus considered unextraordinary) whereas they are less common in straps due to the popularity of the classic pin buckle.

An instrument that measures depth. It typically relies on water pressure and comes in both mechanical and electronic forms. While they are rare in mechanical watches, certain models feature bourdon tube depth gauges. On the other hand piezoresistive pressure sensors are comparatively common and can be found often on digital dive watches.

A dive watch or a person who owns a dive watch that never goes diving. A playfully pejorative term, 'desk diver' makes fun of how many of the buyers of capable and purpose-built dive watches rarely take the watch beyond their office desk. Identical in usage with 'mall crawler' in the automotive world.

(Italian) A nickname for watches that have the crown on the left/nine o'clock position. 'Destro' is Italian for 'right'. The name comes from how these watches are meant to be worn on the right wrist. Other names for these watches include 'LHD', 'lefty', and 'southpaw'.

An escapement which is not connected to the balance, allowing it to swing freely. Examples include the lever, detent, and co-axial escapements.

An escapement that utilizes a detent in the form of a flat spring to engage the balance wheel and train. The detent escapement uses pallet jewels mounted directly on the roller to both receive impulses from the escape wheel and release it. Once in motion, a swing of the balance knocks a jewel on the detent which flicks it away from the escape wheel tooth it is obstructing. The escape wheel turns, during which a tooth knocks the longer outer pallet on the roller, providing an impulse to keep the balance running. This simple mechanism reduces a great deal of friction by having the balance interact directly with the escape wheel (and the rest of the train) instead of using a mediary like a lever. Thus, it requires less lubrication which is good for long-term accuracy. It is also a detached escapement, allowing the balance to swing freely. However, the detent is also a weakness that makes the system vulnerable to timing errors from shocks, bumps, and vibration, and is not self-starting.

The plate which forms the background of a clock on which the time and other information may be displayed. The dial is also called the 'face', 'clock face', and 'watch face'.

A general term that refers to any particular configuration or arrangement of components or design elements on the dial-side, including the dial itself, hour markers, minute markers, and sometimes even the hands. For example, a dial with a bullseye design in black and white is called a ‘tuxedo’ dial. A dial with bullet-shaped hour markers is sometimes called a ‘bullet’ dial. A watch with a Mercedes hand is sometimes referred to as having a ‘Mercedes’ dial, though this use is questionable as the hands are not part of the dial.

The diameter of a dial or clockface. Watches with small dial diameter compared to case diameter usually wear smaller.

A plastic sheet that is placed under the hand stack and over the dial so that the hand removal tool does not damage the dial. The protector is typically a rectangular sheet with a slit down the middle so that the cannon pinion can slide through it.

A bent and tensile ring of metal (copper or brass) which is placed on top of the hour wheel and on the underside of the dial to apply pressure to the hour wheel so that it does not fall out of position. This is because the hour wheel typically sits freely on the cannon pinion.

A style of hands distinguished by a thin base leading to a collar and elongated diamond tip. Diamond hands are typically not lumed.

A style of indices/markers in the form of a rhombus or diamond.

A display which uses numbers to tell the time. Antonymous with 'analog display'.

A watch with a digital display. Antonymous with 'analog watch'. While digital watches commonly refer to electronic watches which display the time with either an LCD or LED, a mechanical watch can also be digital as long as it shows the time digitally, i.e. with numbers, rather than with hands.

An arrangement of center seconds where the fourth wheel is at the center of the movement. This allows the seconds hand to be mounted at the center of the movement with no extra gearing. In a typical arrangement, the second wheel which drives the minutes and hours is set off-center to make way for the fourth wheel, instead utilizing intermediate gearing for the hour and minute hands. Direct center seconds architecture has the advantage of a simpler and thinner arrangement than indirect center seconds. However, in its earliest stages it was costly to completely redesign the layout of the movement.

A nickname for the Rolex Oyster Perpetual GMT-Master II reference 16753 'Root Beer' worn by Clint Eastwood. The watch is also simply known as the 'Clint Eastwood' but is more commonly called by the catchier 'Dirty Harry' who Eastwood starred as in 1971.

(Italian) Flying Saucer. In watchmaking, 'Disco Volante' is a nickname given to wide, flat, and thin watches with particularly round profiles. Many of these watches do not have visible lugs, further accentuating the roundness. The name is most associated with the Audemars Piguet reference 5093 and the Patek Philippe reference 2552. It has also been used for the Omega reference CK2013 and the Jaeger-LeCoultre E562. Also see 'soucoupe'.

See 'exhibition caseback'.

A watch that is meant to be disposed of when its battery runs out or the movement malfunctions.

A category of wristwatch designed to be used underwater by divers. Once essential tools that were crucial for dives, dive watches are now at best backup timers and virtually unnecessary with the advent of dive computers. Nonetheless, dive watches still have strict guidelines governed by standards bodies like ISO and DIN. They are required to have at least 100m of water resistance and must be certified to at least 25% above their claimed water resistance level. In addition they are required to have a function to measure elapsed time, legibility in the dark, resistance to magnetism and salinity, among others. Dive watches are popular due to their distinct design, practicality, and durability. They are also called ‘divers’.

See 'dive watch'. In watchmaking a diver may refer to both a person who dives and a watch that is designed to be taken diving.

A style of hands that is mounted onto dive watches. Diver hands can come in a wide array of styles which all commonly have very broad surfaces to accommodate lume. Diver hands must be lumed.

A style of indices/markers designed for dive watches. Diver markers aren’t a specific design but rather a general term for markers designed for dive watches. As a rule they are geometric and luminous.

A category of wristwatch designed for medical professionals. Medical watches are almost always equipped with a pulsometer and/or asthmometer scale. Sophisticated watches often have chronograph complications to complement the medical scales. These are usually called 'doctor's watches'. The more accessible 'nurse's watches' have a modified seconds hand and/or two of the same scale printed on opposite ends of the dial to make up for the lack of a controllable seconds hand. Both doctor's and nurse's watches have clean, legible white dials.

Short for ‘doppelchronograph’, German for ‘split-seconds chronograph’.

(German) Double chronograph. Synonymous with ‘split-seconds chronograph’.

(German) Double barrel. Literally means 'double feather (spring) house', referring to the two spring housings or barrels. Also see 'double barrel'.

A system of displaying information such as numbers, letters, and symbols by selectively showing dots or pixels. Dot matrix displays are capable of displaying more complex shapes than seven-segment displays and may be able to emulate them if the dot matrix is of sufficiently high resolution. Many digital watches use both the dot matrix and seven-segment displays for different types of information or as a matter of style. Also see ‘seven-segment display’.

‘Dot-over-ninety’ describes a configuration of the Speedmaster tachymeter bezel where the dot marker for 90 is above the number. If not over 90, it is located next to it at the superscript position (90^). While it is a minute detail, a DO90 bezel is characteristic of Speedmasters produced before 1970 and can serve as a key detail in confirming the authenticity of the bezel. Certain modern reissues of pre-1970 Speedmasters convey this characteristic.

A mechanical movement with two barrels means that it can store more potential energy than a typical movement with one barrel. Most double barrels are wound simultaneously by the crown, but some are wound separately with counterclockwise and clockwise crown rotation.

A nickname for models of the Omega Constellation family with two griffes, or claws, on each side of the bezel. The name is a reference to the golf score ‘double eagle’ (American golf terminology for Albatross).

A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 1665 with 'Sea-Dweller' and 'Submariner 2000' in red ink. The Double Red ref.1665 was produced for about a decade until the 'Submariner 2000' line was dropped.

An escapement which utilizes a two rollers, with a ‘safety roller’ stacked on the main roller. A double roller setup divides the roles of a single roller to two rollers. The ‘impulse roller’ serves as the standard roller, hosting the impulse jewel and knocking the pallet fork. The ‘safety roller’ is a smaller-diameter roller stacked below the larger impulse roller and is designed to engage with the guard dart in the event of a strong impact that could throw the escapement off alignment. The smaller diameter of the safety roller allows it to engage the guard dart more efficiently in the event of impact. A double roller can be identified by the lack of a passing hollow cutout on the rim of the main roller table as the passing hollow is on the safety roller underneath.

A variation of the split-seconds chronograph which is capable of splitting the minutes as well as the seconds. Unlike the regular split-seconds chronograph which can only record the difference in two time intervals in seconds, the double split chronograph has a splitting chronograph minute hand which records the elapsed minutes of the split. As the split-seconds chronograph is already an immensely complex complication, the double split is multitudes more difficult to engineer. There is also a triple split chronograph which can split the hours as well.

A Rolex dial with two ‘Swiss’ origin markings, one in the older position outside of the minute track and the other stamped again between the six o’clock marker and chapter ring, where it remains to this day. The Double Swiss stamping is a result of the introduction of the Daytona, which featured a wider bezel than other models (thanks to its tachymeter) that partially covered the original Swiss marking. This led Rolex to double stamp in the new position to ensure visibility. However, other models including the Submariner, Explorer, and GMT-Master may also feature a Double Swiss dial.

The act of wearing at least one watch on each wrist.

A clasp that opens from two ends. Also known as a butterfly clasp.

In watch collecting parlance, 'double-signed' can mean two things. It can mean that a watch is signed with the manufacturer's name in two places, usually the dial and movement. This use is more common when discussing pocket watches. The more common definition means that the watch bears two different signatures on the dial, usually by the manufacturer and retailer. Double-signing is a rare occurrence these days and retailer signatures from certain reputed jewelers and watch sellers may command high prices. Also see 'retailer signature' and 'triple-signed'.

A category of wristwatch distinguished by its classical and conservative form factor. Some define the dress watch as a watch designed to be worn with formal dress, which may also be an appropriate definition. Pinpointing the exact parameters of a dress watch is quite difficult as the dress watch is the quintessential and oldest style of wristwatch, dating back to an era when even military uniforms were formal by the standards of today. The dress watch is defined purely by aesthetic instead of function, and especially pertains to the case profile and somewhat less to the dial features. Generally it is agreed that a dress watch case prefers simple and elegant lines and surfaces with minimal protrusions such as pushers, crown guards, or ears. They are meant to be unobtrusive and subtle, usually coming in a smaller case size and a leather strap which minimize the presence of the watch and allow it to slide under a dress cuff. Nonetheless, any watch can be a dress watch as long as it looks 'dressy'.

Deep Reactive Iron Etching. A manufacturing process that is used to manufacture small components out of silicon wafers with high precision through lithography and plasma etching.

The deviation in a clock's accuracy, particularly in the context of quartz movements.

A type of lug whose spring bar hole is drilled all the way through the lug. Drilled lugs can be identified by the holes on the outer faces. The outer holes make spring bar removal much easier as a simple poke of a spring bar tool through the hole is enough to depress the spring bar head.

A hook which grabs a tooth on the side of the rack and drives it to make a sound. Which tooth the hook latches onto determines the number of chimes as it dictates how many teeth on the bottom of the rack pass through the hammer trip.

A category of wristwatch designed for driving. Driving watches were particularly popular in the 1970s as quartz watches with sideways digital displays. Today the category encompasses watches that pay tribute to automotive culture and those inspired by automobiles. While it is a relatively niche genre, the large overlap between watch and car enthusiasts makes the driving watch a cult favorite.

A component of a chronograph mechanism which is co-axially mounted with the fourth wheel of the movement via an extended pivot.

The practice of selling products that the seller does not physically have in stock, instead putting in the order on the buyer’s behalf to the manufacturer which the seller typically has no affiliation with. In the watch world, the term specifically refers to the practice of ordering generic unbranded watches from (usually overseas) factories, applying a company logo, and selling them to consumers. As the seller running the brand has little if any involvement with design, production, and distribution, the seller is occupied entirely with marketing. Dropshipped watches typically rely on exaggerated marketing and deceitful brand image building to sell cheap watches for multiple times their original price from the factory and target the non-enthusiast public.

A complication that displays another timezone. The terminology is vague, as it technically includes the more specific and better-known GMT complication. In common usage, a dual time complication is one that displays both the hours and minutes of the second time zone. The minute hand on the second time zone subdial is usually synchronized to the regular minute hand. When it is not, a dual time complication becomes capable of displaying timezones offset in sub-hour increments such as Indian Standard Time. As the second time zone hour hand is typically a 12-hour hand, dual time watches come with day/night or am/pm indicators.

A handheld silicone or rubber air blower that is used to blow dust and lint off a movement.

A timepiece's ability to stop dust from entering the case. Dust resistance was a concern during the times when the internals of the watch were frequently exposed, such as open face pocket watches and holes for winding and setting keys. Today, dust resistance is not as much of a concern as watches are almost completely sealed off. Thus it is rarely mentioned.

A time correction value that represents the difference between UT1 (Universal Time 1) and UTC (Coordinated Universal Time). Expressed as DUT1 = UT1 - UTC, this value indicates how much UT1 deviates from UTC, typically by fractions of a second. DUT1 helps align precise rotational time (UT1) with standardized civil time (UTC) and is broadcast by timekeeping services to allow for real-time corrections in applications that require synchronization with Earth's rotation. When DUT1 reaches ±0.9 seconds, a leap second is added or subtracted from UTC to bring it back in close alignment with UT1. This leap second is a key characteristic of UTC and its suitability as an international time standard.

A type of numerals featured on watch dials, also called Mashriki numerals or Indo-Arabic (ʾarqām hindiyyah) numerals. They are genetically related to the more famous western Arabic/Ghūbar numerals, both having descended from the Hindu number system. While western Arabic numerals gained international use after further evolution in medieval Europe, eastern Arabic numerals remained contained to the eastern Arab world or 'Mashriq', hence the name. In watchmaking eastern Arabic numerals are considered a novelty or a region-specific feature.

A quick adjustment extension system mounted onto certain Rolex Oyster and Jubilee bracelets. Easylink utilizes folded half-links towards the anchor which can be unfolded to give 5mm of extra bracelet length. This simple system is Rolex’s most widespread quick extension system due to its compactness.

(French) Literally means blank, sketch, or outline. In watchmaking the term refers to a usually incomplete and/or unassembled watch movement that is sold to other companies which will assemble and/or complete the movement and put it in a watch. In the past, ébauches included plates, bridges, gear train, and winding mechanism but not the escapement, balance, or mainspring. Today, the term is used more loosely and refers to any blank movement that is meant to be modified, regulated, branded, and fitted to a watch by another watch brand, regardless of the completeness of its components. See 'third party movement', 'in-house movement', and 'proprietary movement' for comparison.

In mechanical engineering, an eccentric is a disk that is fixed to an off-center rotating axle. In watchmaking, especially in chronographs, ‘eccentric’ refers to an ‘eccentric stud/screw’. See ‘eccentric stud/screw’.

A component of a chronograph mechanism which is a screw-headed stud that fastens several important levers of the chronograph. They are more commonly referred to as ‘eccentrics’. These studs can be adjusted to finely tune the operation of the chronograph and may cause severe friction and wear if poorly fiddled with.

Military timezone name for UTC-5.

A brand of light-powered quartz movement produced by Citizen.

A nickname for the Omega Speedmaster reference 105.003 and its modern descendant the reference 311.30.40.30.01.001. The ref.105.003 is named after American astronaut Edward White II, who wore two of these watches on the first American extravehicular activity, or spacewalk, in 1965. The ref.105.003 was the first Speedmaster to be approved by NASA by for all manned space missions and introduced the baton hands that would become standard for all subsequent Speedmasters. The 2020 ref.311.30.40.30.01.001 which heavily references the ref.105.003 and carries the same cal.321 movement is also called the Ed White.

(Italian) Egyptian. There are several timepieces that bear the ‘Egiziano’ nickname, the most famous probably being the Panerais produced for the Egyptian Navy. The much lesser known Egiziano is the Longines C.O.S.D. watch with the so-called ‘Egyptian’ numerals.

(Spanish) A nickname for the early examples of the Rolex Oyster Perpetual GMT-Master 1675 featuring pointy crown guards (PCGs). The name is a reference to how the PCGs look like horns. Also see ‘PCG’.

A type of hybrid movement which existed primarily in the 1950s and 1960s. Electric movements utilize the electric current from a battery to power the action of a traditional balance spring or a tuning fork which vibrates upon receiving a charge. Electric watches were rendered obsolete by the introduction of purely electronic watches which utilized quartz crystal timing packages which were far more accurate.

One of the three major types of movements. Electronic movements use an electrical power source such as a battery or capacitor to power an electronic timekeeping device like an integrated circuit/microchip. Virtually all electronic movements are quartz movements which use a quartz crystal to serve as a timing reference. Thus, the term 'quartz movement' is a far more widely used and recognized term.

(French) Enamel.

Émeraude. Rolex nomenclature for a bezel set with baguette cut emeralds.

(French) See ‘in passing’.

A glassy coating baked onto ceramic or metal surfaces. Enamel can be both a decorative and practical technique. In watchmaking, enameling is widely used on dials for decorative effect. The most common variety is vitreous enamel which can be applied to various techniques such as cloisonné, flinqué, and champlevé.

Links (metal components of a bracelet) that connect the rest of the bracelet to the watch head. End links may be a single component or may consist of several interlocking components. Not all bracelets have end links and some straps have end links. End links allow for a seamless connection between the head and band. Also see 'solid end link' and 'hollow end link'.

A nickname for the Audemars Piguet Royal Oak Offshore reference 25770SN. The watch was designed with input from bodybuilder, actor, and former governor of California Arnold Schwarzenegger as he was to wear it in the 1999 film End of Days.

The vertical tolerances of a jewel. An example of endshake would be the travel distance of a pivot in relation to the jewel it makes contact with. Appropriate levels of endshake are necessary for watch parts to move properly, minimize friction, and/or absorb shocks. Excessive endshake may result in disengagement of a watch component with its jewel. Insufficient endshake may slow down or seize the watch by causing excessive friction. Also see ‘sideshake’.

In watchmaking, an engine is a mechanical device that engraves patterns, typically on a metal workpiece. Engines make stable cuts into the workpiece, producing uniform and precise engravings that are ideal for repetitive patterns. The two most common types of engine in watchmaking are the straight-line engine and the rose engine lathe. The straight-line engine is typically used for straight and linear patterns. The rose engine lathe can move its cutter more dynamically, allowing it to make wave-like, undulating patterns.

A style of Rolex bezel that features a mix of engine-turned radial grooves and large tabs. There are largely two styles for the engine-turned bezel. One features large tabs that correspond to the hour markers on the watch, with a double tab for the 12 o’clock marker. This gives it a total of thirteen tabs in twelve positions. The other features a much greater number of thinner tabs that correspond to each minute marker interspersed with the grooves, resembling a fluted bezel at first glance. This gives it sixty tabs.

A finishing technique of mechanically engraving patterns onto a surface (usually metal) using a machine called an ‘engine’. The patterns are created by removing metal from the workpiece as opposed to stamping, molding, or grinding, and are done by a machine as opposed to by hand. Engine-turned patterns are almost always repetitive, and are typically radial and intersecting. They often resemble circular patterns created by a spirograph. Certain engine-turned patterns are not radial - these are usually created by a straight-line engine instead of the more famous rose engine lathe. Engine-turning is commonly referred to as ‘guillochage’ and even more commonly as ‘guilloché’.

A now-obsolete style of the lever escapement. The balance wheel and lever form one axis that is perpendicular with that of the escape wheel. In the English lever escapement, the lever is I-shaped, with one end of the I flat and the other having a swallowtail cut to engage the impulse pin on the balance wheel. The two pallets are mounted on one side of the I. The escape wheel teeth are different as well, as English escape wheels have sloped spike teeth. While the lever escapement is an English invention, the Swiss lever escapement eventually replaced it in virtually all mechanical movements.

A type of leather. It refers to top grain leather from the top of the animal's hide that has been treated for imperfections and blemishes and stamped with an artificial grain print.

A de facto defunct watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1914. Enicar was declared insolvent in 1987 and its assets and name were sold to different companies. The name is owned by Wah Ming Hong Ltd.

A pallet jewel on one end of the pallet fork which is the first to contact an escape wheel tooth. The entry pallet is typically mounted on a shorter arm and is angled more gently than the exit pallet.

‘End of Life’. An EOL indicator is a feature on a quartz timepiece which signals that the battery is at the end of its life. Whereas mechanical timepieces can simply be wound to replenish the power reserve, quartz timepieces cannot function at all without a battery. Hence, an EOL indicator is an important feature for quartz watches. In digital watches with LCD/LED display, an EOL icon will appear. In analog watches, the seconds hand typically leaps two hash marks every two seconds (instead of one every second) to get the owner’s attention. EOL indicators are mandatory for quartz dive watches.

A historical time standard established in the mid-20th century to provide a uniform, precise time scale for astronomical calculations, based on the motion of celestial bodies rather than Earth's rotation. Created to address irregularities in Universal Time (UT) due to variations in Earth’s rotation, Ephemeris Time provided a consistent reference for the positions of planets and stars as determined by their predicted orbital paths (ephemerides). ET was eventually replaced by more accurate atomic time scales like Terrestrial Time (TT) and Barycentric Dynamical Time (TDB).

The difference between apparent solar time and mean solar time. Apparent solar time is based on the actual movement of the sun, which varies because of Earth’s elliptical orbit and tilted axis of rotation. Mean solar time is time that is kept by humans based on the assumption that each day is exactly twenty-four hours long. Also see ‘apparent solar time’, ‘mean solar time’, and ‘equation of time (complication)’.

An astronomical complication that indicates the equation of time. It is usually a circular sector with a hand that indicates the equation of time between +15 and -15 minutes on a scale.

A dial configuration with a combination of Roman, Arabic, and geometric numerals. Originally created and named by Rolex, the dial configuration is now more commonly known as a ‘California dial’. The original error-proof dial has a diver-style triangular marker at 12, rectangular markers at 3, 6, and 9, Roman numerals at 1, 2, 10, and 11, and Arabic numerals at 4, 5, 7, and 8.

A component of the going train that is the fifth and final wheel to transfer energy from the unwinding of the mainspring. It is also a component of the escapement. The escape wheel interacts with the fourth wheel pinion and knocks the pallet fork, which knocks the balance wheel via the impulse jewel. The escape wheel is designed so that it interacts with the pallet fork to seize the going train until the impulse pin comes back to strike the pallet fork and free the escape wheel, allowing the movement to advance. This continuous cycle of seizing and releasing the going train is what determines the speed of the movement. To fulfill this role, the escape wheel is markedly different from the other wheels of the going train as it has heavily slanted club-footed teeth.

In a general sense, an escapement is a mechanism that regulates the motion of other components, typically by locking and releasing a moving part. In watchmaking, an escapement is a mechanical linkage that regulates the motion of the gear train at a speed determined by the timekeeping mechanism. Escapements have existed in various forms throughout history, with fluid-driven escapements likely acting as the first reliable systems until verge escapements appeared in 13th century Europe.

(French) A general term for the manufacturing process of a timepiece from readymade components, specifically concerning how an ébauche and unassembled components are received, assembled, tested and timed, cased, and dispatched. ‘Établissage’ is French for ‘workbench’.

(French) A factory or individual who buys components from suppliers, usually to assemble but sometimes also to finish or modify. An établisseur may outsource the actual terminage work (assembling the watch) to an atelier de terminage.

A watch manufacturer established in Grenchen, Switzerland in 1856. Eterna is owned by the Citychamp Group.

(French) A Genevan French term for a banking pin. See ‘banking pin’.

A nickname for radium Rolex dials of the early 60s (mostly 1962) which feature a dot on the minute hash below the six o’clock baton marker, making the pair look like an exclamation point. This is an indication that the watch is compliant with then-new radiation regulations from the Atomic Energy Commission, and features less radium than before. Rolex’s radium dials ceased production in 1963, which ushered in the transitional tritium conversion dials. Also see ‘underline dial’ and ‘T < 25’.

A caseback that has a crystal window that provides a view of the movement. Also known as a clear caseback or sapphire caseback.

A pallet jewel on one end of the pallet fork which is the second to contact an escape wheel tooth. The exit pallet is typically mounted on a longer arm and is angled more steeply than the entry pallet.

A variation of a dial that is usually rarer, quirkier, and/or more experimental than the main variant. The most famous exotic dial is perhaps the one mounted on the Rolex Cosmograph Daytona reference 6239, which would later be called the ‘Paul Newman’ dial.

A nickname for Universal Genève Compax references 885107 and 885108 ‘Nina Rindt’ chronographs with exotic dials.

A bracelet that can be stretched. Some expansion bracelets stretch only a modest amount while others can contort like a slinky. Also see 'rivet bracelet' and 'Twist-o-flex'.

A category of wristwatch designed for expedition, exploration, and adventure on land. The category is somewhat vague but it includes famous types of watches like mountaineering/alpinist watches, spelunking/cave exploration watches, and expedition watches. They can be understood as the civilian counterpart to the famous field watch. Generally these watches have high visibility at night, shock and water resistance, and often have tools useful for navigation like a compass, altimeter, or barometer.

A style of numerals - mostly Arabic - where the numerals begin towards the center of the dial and stretch out to the corners of the dial. The radial composition and the exaggerated size of the numerals gives the impression that the numerals are exploding outwards. Exploding numerals are typically seen in rectangular watches and are almost always painted or printed, not applied. It is one of the most distinctive styles of numerals in Art Deco watch design.

See 'oversize(d) watch'.

Short for ‘extract from the archives’.

A document detailing the date, location, and other details of a timepiece’s manufacture and retail issued by the original manufacturer of a timepiece at the request of an individual. This document usually applies to older timepieces and can serve as an important piece of paperwork for vintage watches whose original documentation is usually lost. Extracts are not certificates of authenticity because obtaining an extract rarely requires more than photos and movement/case serial numbers. However, an extract will at least demonstrate that the serial number of a movement is valid. Information on certain extracts will allow the recipient to discern modifications done on their watch. Therefore, while an extract is not a suitable proof of a watch’s authenticity, it is still good to have. It should be noted that most manufacturers do not provide this service.

A watch manufacturer established in Geneva, Switzerland in 1999. Abbreviated ‘FPJ’. F. P. Journe is privately owned.

(French) Short for 'Fabriqué en Suisse'. Means 'Made in Switzerland'. Also see 'Swiss Made'.

A strap that is made of fabric such as nylon, canvas, sailcloth, cotton, etc. Composed of either one piece or two pieces.

Synonymous with ‘dial’.

A style of lugs, usually tapered, distinguished by flat faceted surfaces instead of curved ones. Whereas the top side of a tapered lug gently curves downwards to the tip, faceted lugs replace the curve with two or three flat surfaces. This style of lugs was famously used in many cases made by Spillmann & Co. which supplied cases to numerous named brands in the mid-20th century. Hence, these lugs are sometimes called ‘Spillmann lugs’.

When something is described as 'factory' in watchmaking, it means that it is the way it came from the factory, without modifications done by a third party. A comparable term is 'stock' in the automotive world. The term is especially used to describe interesting, quirky, or rare features of a watch that are worth mentioning such as gem settings, unique colors, or engravings that were approved and executed by the original manufacturer of the watch. It is antonymous with 'aftermarket'.

(Italian) Little bean. A style of lugs that have a curved oblong profile reminiscent of a bean. The name likely arose from the lugs of the Patek Philippe reference 591.

An inauthentic timepiece that presents itself as authentic. While plenty of watches outright copy the design of others, they are technically not fake until they brand the watch with a fake logo and brand. See ‘homage’. A watch may even be composed of certain real parts, but presenting it as wholly authentic makes it fake. See ‘frankenwatch’. Generally, fake watches refer to copies of existing watches sold to scammers who defraud buyers who expect an authentic watch, or to posers who buy the watch to flaunt it as if it were real. See ‘replica’, ‘clone’, and ‘super clone’. Many fake watches are not copies of existing models, but rather anything from a borderline accurate copy to a completely made-up design with fake branding.

A catchall term for flamboyant and unconventional lugs styles.

A term, often derogatory, for a watch that is either (i) sold under a fashion brand, or (ii) made by a brand whose watches focus more on generically popular designs than watchmaking. While the term is broad, it usually refers to cheap watches that are produced for retail at high markup by famous brands typically to the general public and not watch enthusiasts. Some more extreme uses of the term include some watches produced by brands that don’t focus solely on watches such as jewelry brand Cartier and fashion brand Hermes.

A nickname for the Rolex Oyster Perpetual GMT-Master II reference 16760, a GMT-Master II with a black and red aluminum bezel and red GMT hand. The name 'Fat Lady' is a reference to the beefy case that was needed to accommodate the upgraded movement, which was the first iteration of the GMT-Master II that could display one more timezone than the GMT-Master and had an independently-adjustable hour hand. The watch was also dubbed the 'Sophia Loren' for the same reason and the 'Coke' for its colors.

(French) Fake. In watchmaking the term typically describes non-functioning or unoriginal components that exist purely for cosmetic appearance. They are particularly common in watches that reference vintage designs.

Metal rivet heads attached to the side of an outer link to mimic the appearance of a riveted bracelet.

A surface treatment or color that is meant to simulate patination. A portmanteau of the French word 'faux' (fake) and 'patina', sometimes used in a derogatory fashion. Fauxtina is especially popular for lume plots as the creamy yellowish lume of vintage watches is desirable.

The hooked end of a rack in a repeater. The feeler interacts with the levels/steps on the snail cam.

Watch collecting slang for a fake Seiko watch.

A style of dial in railroad pocket watches that features the following: an indication of the hours from 1 to 12 in medium-sized bold red Arabic numerals towards the center of the dial, an additional ring of the five-minute markers in large bold black Arabic numerals, and sometimes a ring of red Arabic numerals repeating the numbers from 0 to 9 six times outside the minute markers. It was designed by Louis B. Ferguson and patented in 1908.

A ceramic material with ferrimagnetic properties. Rare in watchmaking, it is sometimes used to make dials.

See ‘leaf hands’.

A category of wristwatch designed to be used by soldiers fighting on land. Field watches were arguably the first men's wristwatches as they were born out of a need to keep a timepiece on the wrist instead of the pocket during the wars of the 19th century. The field watch as we understand it today is largely based on designs from the 1950s to 1970s when wristwatches with highly legible dials, rugged reliability, and cheap cost of manufacture were standardized, ordered, and issued by the militaries of the world. However there is still variety within the field watch category, such as the classic trench watch, officer's chronograph, and digital field watch.

A tool with an abrasive surface that is used for filing down surfaces.

See ‘baton hands’.

A particularly long leaf or protrusion, especially on a wheel or pinion. Fingers are useful for transforming continuous movement to periodic movement.

See 'finger cot'.

A latex or rubber cover worn over one or more fingertips to prevent contamination. In watchmaking, finger cots are useful for watchmakers whose dexterity may be negatively affected by a full latex glove or when only a select few fingers need be covered. Finger cots prevent natural oils produced by the human body as well as other contaminants carried by the hands from coming into contact with surfaces on a watch, especially the movement. They are more commonly known as 'finger condoms'.

The manner in which a surface has been finally treated. Finishes can be done for both practical and aesthetic purposes.

A component of the going train that is the first wheel to transfer energy from the unwinding mainspring to the rest of the motion works. The first wheel is in fact the mainspring barrel itself, as the barrel is lined with teeth that make it a wheel. It is also known as the ‘great wheel’.

A striking complication that repeats (chimes) the hours and every five minute interval that has elapsed since the last hour. Typically the hours are sounded with a bass note and the five minute sections with a treble note or one of each.

A type of bar that is permanently fixed in position. Fixed bars may either be designed as such or soldered on later. They resolve the small but extant failure risk that spring bars have. The tradeoff of fixed bars is that they can only receive one-piece straps such as natos and zulus or antiquated leather straps that loop around the bars. Fixed bars are commonly found on military watches.

A style of lugs that resemble a flame. The term is somewhat broad, but a flame lug generally resembles a curved twisted lug with additional decorative bolstering on the outer side.

See ‘foudroyante seconds’.

A nickname for a variant of the Rolex Oyster Perpetual Submariner 16610LV ‘Kermit’ which features a noticeably flat and wide top on the number ‘4’ in 40-minute marker of the rotating bezel. Perhaps the best-known variant of the Kermit, the Flat Four is a distinguishing mark of the first series of Kermits produced. Because the Kermit is a 50th anniversary model for the Rolex Submariner, the Flat Four is regarded as the ‘true’ anniversary model as it was released in the actual anniversary year.

The later variation of the Rolex Kermit Flat Four which does not feature any serifs on the bezel numerals. The Sans-serif font itself would become standard for all later iterations of the Kermit.

The earlier variation of the Rolex Kermit Flat Four which features small serifs on the bezel numerals. The Serif was soon replaced by the Sans-serif or Non-serif Flat Four.

A three-link bracelet with wide center links, narrow outer links, all with a very short and completely flat profile. Flat link bracelets were made by Omega for the Omega Speedmaster.

A style of lugs that do not curve downwards to conform with the shape of the wrist. Flat lugs are typically stubby.

A nickname for Rolex Oyster wristwatches with a manually-wound movement. The nickname is a reference to the flatness of the caseback relative to the similar but automatically-wound ‘Bubbleback’ watches. The lack of the oscillating rotor eliminated the need of the protruding Bubbleback caseback.

A nickname for Rolex Bubbleback-style Oyster Perpetuals that were offered with a manually-wound movement. The lack of an automatic winding mechanism eliminated the need for the bulbous caseback which gave the Bubbleback its nickname. Hence, these watches were called Flatbacks.

Watch collecting social media lingo for the reflections on a watch crystal. Different crystal materials and shapes produce vastly different types of reflections.

A style of hands distinguished by fleur-de-lis-shaped tips. Fleur-de-lis hands are not lumed.

A nickname for the Seiko Flightmaster family.

(French) A decorative technique where vitreous enamel is poured onto a guilloched/engine turned surface, usually a dial. The vitreous enamel pools in the grooves of the engine turned dial, resulting in a beautiful end product where the engine turned surface is visible under a translucent layer of glassy enamel. Flinqué is highly desriable because it marries two highly respected techniques and because faulty dials cannot be corrected, only remade from scratch.

The act of selling a watch that was purchased purely for the expectation of selling at profit rather than personal use. Flipping is done with watches that trade at or are expected to trade at a value that exceeds the MSRP. A person who flips watches is called a ‘flipper’.

A quick adjustment extension system mounted onto certain Rolex Oyster bracelets. Fliplock utilizes foldedn links towards the anchor which can be unfolded to give 26mm of extra bracelet length. Fliplocks are usually paired with Glidelocks to provide maximum extension on heavy duty dive watches which need to fit over thick diving suits.

A person who routinely flips watches for profit.

See 'surprise piece actuating lever'.

A decorative finishing technique that involves the use of grooves. There is no clear distinction between the many techniques that use grooves, but fluting typically refers to sharper, triangular grooves instead of rounded grooves. Also see ‘coin edge’ and ‘reeding’.

A mechanism which rapidly resets a hand to its default position without having to stop it first. Also see ‘flyback chronograph’.

A chronograph that is capable of resetting to zero without first stopping. In a normal chronograph, pressing the reset pusher while the chronograph is still in operation will do nothing or damage the movement. A flyback chronograph will always reset the chronograph at any time, regardless of whether the chronograph mechanism is in use. This allows the flyback chronograph to time two consecutive and separate events without delay. Additionally, the flyback mechanism makes the chronograph virtually ‘unbreakable’ as the pushers can be pushed in any order whatsoever with no damage to the movement.

A component of a chronograph mechanism which allows a flyback chronograph to reset the chronograph without first stopping it. Essentially, the flyback chronograph combines the stopping, resetting, and starting procedures into one and this is made possible by the flyback lever. The lever is connected to the reset lever and the coupling wheel bridge/clutch bridge or the coupling arm. Pushing the reset pusher moves the reset lever, which pushes the flyback lever via a stud or some other form of contact which in turn pushes away the clutch wheel from the chrono runner. This decouples the chronograph mechanism from the movement’s power delivery (stop) and allows the reset hammers to knock the chronograph wheels back to zero (reset). Finally, releasing the reset pusher recouples the clutch, resuming power delivery to the now-reset chronograph runner (start).

A component of a chronograph mechanism which is a slightly modified reset lever to fit the functionality of a flyback chronograph. Unlike a regular reset lever, the flyback reset lever does not have a finger or beak that pushes against the wall of a column wheel pillar. In a normal chronograph this finger is a safety feature that prevents the reset lever from activating when the chronograph is running. This is obviously not needed in a flyback. Another modification is the addition of a stud which pushes the flyback lever.

A style of watch case distinguished by a thin, flat, wide, and circular profile, often without visible lugs in order to complete a perfectly circular silhouette. In watch collecting parlance, the style is more commonly referred to by its Italian name, ‘disco volante’ and less commonly by the French name ‘soucoupe’.

A nickname for the Omega Speedmaster reference 2998 and the various watches inspired by it since 2012. The nickname FOIS which stands for ‘First Omega in Space’ comes from the fact that the ref.2998 was worn by American astronaut Walter Schirra during the 1962 Sigma 7 mission, making it the first Omega watch to leave Earth. It is also called the ‘Wally Schirra’ in honor of the man himself. Various modern Speedmasters that reference the aesthetics of the ref.2998 are dubbed FOIS as well. They share alpha hands, symmetrical case, smaller size, applied logo, and other details that do not exist in the modern Moonwatch which is largely based on the aesthetics established in ref.105.012.

A horn at the fork end of the pallet fork. A pallet fork has two fork horns and usually a guard dart attached between the two horns.

(French) Lightning. In watchmaking, the term refers to foudroyonte seconds. See ‘foudroyante seconds’.

A complication wherein the seconds hand is engineered to display fractions of a second through a hand that completes a full rotation every second instead of every minute. Technically, any mechanical watch inherently shows fractions of seconds because it beats several times (usually between 5 to 10) a second. However, these fractions cannot be read because they occupy a microscopic segment of the seconds track. A foudroyante seconds makes these fractions more legible by having a dedicated seconds subdial with a seconds hand that makes a full rotation every second. For example, for a watch that beats 10 times a second, each tenth of a second would be allocated 0.6 degrees on a conventional dial whereas it would get 36 degrees on a foudroyante seconds subdial. Having such a short rotation cycle means that the foudroyante seconds hand jumps around the subdial at lightning-fast speeds, having to cover multiple times the distance a normal seconds hand would. ‘Foudroyante’ is French for lightning.

A component of the going train that is the fourth wheel to transfer energy from the unwinding of the mainspring. A coaxial pinion meshes with the third wheel, turning the fourth wheel once every minute. Therefore the fourth wheel mounts the second hand. In many modern center-seconds movements, the fourth wheel is moved to the center of the movement so that the seconds can be displayed at the center of the dial. In this case, the fourth wheel becomes the center wheel instead of the usual second wheel. On the other end, the fourth wheel interacts with the escape wheel.

Military timezone name for UTC-6.

(1957-) A watchmaker hailing from Marseille, France and based in Geneva, Switzerland. François-Paul Journe is the mastermind behind watch manufacturer F. P. Journe.

See 'frankenwatch'.

A timepiece that contains parts from various donor timepieces, especially from different manufacturers and/or eras. A timepiece whose parts are replaced with correct factory-made parts - even those taken from another watch - is typically not deemed a frankenwatch. A timepiece whose parts are replaced with official factory parts that are not correct to the watch itself may or may not be considered a franken depending on the extent of the modification - a small gear in the movement will likely not warrant the frankenwatch designation by most collectors but a whole replacement dial certainly will. The term is most commonly used in the vintage watch scene as it deals with watches from an era with countless obscure and poorly documented special-order watches, as well as fanciful and often surprisingly true anecdotes. Frankens aren’t always malicious, and are not necessarily ‘fake’ until they are sold as authentic. Some vintage hobbyists create their own frankens in the same way that modern watches are ‘modded’.

An online watch publication based out of the Hague, the Netherlands.

(Italian) Large arrow. A nickname for the Rolex Oyster Perpetual Explorer-II reference 1655, whose large orange 24-hour hand resembles an arrow. It is the less popular but far more accurate nickname than 'Steve McQueen', which the ref.1655 is more commonly called.

See 'free sprung balance'.

A balance that does not have a dedicated regulator to adjust the free length of the balance spring. A free-sprung balance has a fixed hairspring length and is instead adjusted by moving the timing screws, inertia weights, or other components on the balance wheel. Free-sprung balances are usually more finely adjusted from the factory and eliminate the variable of spring length. They are thus less susceptible to changes in adjustments by shocks and are more accurate when adjusted correctly. However, they are more complicated to work with than an index-adjusted balance.

In watchmaking, frequency is the number of actions a timekeeping organ performs over a fixed period of time. It can be used to describe the frequency of any movement type including both mechanical and quartz. Units of frequency can be Hertz (Hz), beats per second/minute/hour (bps/m/h), or vibrations per second/minute/hour (vps/m/h). Also see ‘beat rate’ for a frequency measurement specific to mechanical balances.

An object that moves at a constant and reliable frequency that functions as a reference for timekeeping. A frequency reference is necessary for any timepiece that functions independently of environmental factors like the sun (for sundials). Examples of a frequency reference include pendulums, balance wheels, tuning forks, quartz crystals, an cesium atoms. Also see ‘timekeeping organ’.

A squishy rubber ball that is designed to open casebacks, especially screw-down casebacks. The friction ball is an excellent way of opening screw-down casebacks without scratching or chipping the caseback, and is sufficient for most casebacks unless they are firmly tightened.

A rotating bezel that has a smooth action with no discernible steps or clicks. Friction bezels are fitted on top of a wave spring, a circular flat spring with wave-like bends that give it the properties of a spring. The wave spring's purpose is to provide some amount of resistance so that the bezel does not spin whenever the watch is moved. Friction bezels have the advantage of being able to stop anywhere. Also see 'click bezel'.

A clasp that uses sheer friction between its components to lock. As they have no button or latch to release the locked hinge, the wearer must pull the clasp open by force. Friction clasps are generally thinner in profile, simpler, and some would say more reliable than push button clasps.

‘For Sale’. Watch collecting social media abbreviation to indicate that a watch is available for purchase. Also see ‘NFS’.

A nickname for the Rolex Oyster Perpetual GMT-Master reference 1675 with a distinctly faded and discolored aluminum bezel where the red turns into a pinkish fuchsia. Fuchsias are highly desirable for their beautiful discolorations and were only made for a short period of time before Rolex changed their paint to a more resilient one. Hence, many Fuchsias are faked or bezel-swapped. Particularly pink Fuchsias are also called ‘Pink Panthers’.

(Japanese) Pufferfish. A nickname for the Citizen NY0XXX series divers, named so for their spiky bezel that resembles a pufferfish.

(Japanese) Barnacle. A nickname for the Citizen 62-6198 Challenge Diver and its modern reissues of the Promaster NB6021 series. The nickname comes from a 62-6198 found washed up on a beach in 1983 after being thrown around the ocean floor long enough for barnacles to engulf the watch. The watch was still running when it was discovered. Also see 'Fujitsubo (Seiko)'.

(Japanese) Barnacle. A nickname for all Seiko watches with a fujitsubo/helmet-style case, an oblong-profile case with integrated sloping lug hoods. This includes the Seiko 6139-710X series automatic chronographs and the Seiko 5 Sports Speed-Timer reference 6138-0020 automatic chronograph. Also see 'Fujitsubo (Citizen)'.

A type of leather. Full grain leather is generally regarded as the highest grade of leather. It comes from the very top of the animal's hide. As the name implies, it retains the characteristics of the leather intact. It is very durable and long-lasting.

The state of having all the furniture, documentation, accessories, and extra parts that came with the watch upon initial delivery. In addition to box and papers this includes extra bracelet links if any, warranty card if any, hang tags if any, and tools and loupes if any.

See ‘diamond hands’. ‘Fuseaux’ is French for ‘spindle’.

(French) A conical pulley with helical grooves that accommodate a chain which is connected to the mainspring barrel. The fusée is mounted on an output gear through which it transfers energy from the mainspring to the going train with minimal variation. Also see 'fusée-and-chain' and 'constant force mechanism'.

A mechanism consisting of a fusée and mainspring connected by a roller chain which evens the force output of an unwinding mainspring and delivers even force to the wheel train. The fusée-and-chain is a constant force mechanism that replaced the stackfreed. The unwinding mainspring turns its barrel housing which pulls on the chain, unwinding it from the helically-grooved conical fusée which spins and activates the wheel train via a toothed wheel fixed on top of it. The exact profile of the fusée is engineered to the mechanical properties of the mainspring, but all fusées are narrower at the top as the mainspring barrel will pull with the most torque when the mainspring is fully wound. The increasing diameter of the fusée as the chain unravels makes the resistance correspond to the torque of the mainspring. When the mainspring is at minimal torque, the fusée’s diameter is at its widest, its resistance at its smallest. The fusée-and-chain was mostly replaced by the toothed mainspring barrel by Lépine.

A brand of highly durable and shock resistant watches owned by Casio.

‘Go anywhere, do anything’. A GADA watch is a durable timepiece that is capable of accompanying its owner to any environment from the office to the seas. A GADA watch is often the choice for a one-watch collection. Also see ‘one-watch collection’.

A finishing technique and decorative pattern that yields a series of convex curves. On three-dimensional surfaces, gadrooning may involve a series of convex curves or alternating convex and concave curves, giving the appearance of flower petals. On two-dimensional surfaces, gadrooning often yields a radial pattern of wavy lines in relief, vaguely resembling the gadrooning of three-dimensional surfaces. In watchmaking, gadrooning may be used as a dial-finishing technique or to embellish external components such as the crown, case, or bracelet. It is relatively rare sight in watchmaking.

A nickname for certain examples of the Rolex Oyster Perpetual reference 6098 which feature hour markers in the shape of five-pointed stars. Also see 'Stelline', a ref.6062 Triple Calendar with the same indices.

In watchmaking, a galvanized surface is one that is covered in a paint that has been galvanically applied, i.e. using electrical processes akin to electroplating gold. The technique was used predominantly on dials meant to have gilt features. Also see 'gilt dial' and 'galvanized gilt dial'.

A dial, usually copper or brass, whose plate is highly polished and/or covered in gold leaf which is exposed through layers of galvanically-applied paint through negative relief. The process can be done in two ways: the first being the etching of the paint to reveal the substrate and the second being the application of a transparent coating of the dial features before the paint is applied so that the paint does not stick. The latter process is more common and usually allows for more intricate and accurate patterns to be created via pad printing. The paint (which becomes the dial color) on top of the coated areas disappears when it is washed off or baked, revealing the dial plate's color. The baked product is then treated to a coating of glossy lacquer that seals in the dial and prevents oxidation of any exposed dial plate. Thus this dial style is often referred to as 'glossy gilt dial' or 'glossy galvanized dial'. The galvanized gilt dial is the most famous and iconic type of gilt dial, with many regarding o

A deformable mechanical seal meant to provide sealing under compression between two married surfaces. In watchmaking it is interchangeable with the term 'o-ring', which is technically just one of the many types of gaskets. Gaskets are usually made of rubber or silicone and serve as important seals against water leakage and humidity. They can be found in virtually every orifice of a water resistant watch such as the crystal opening, caseback opening, and crown assembly.

A defunct manufacturer of wristwatch bracelets established in Geneva, Switzerland in 1835. Gay Frères is indisputably one of the most important and prolific bracelet manufacturers in history, and is responsible for dozens of designs that still dominate the market today. Some Gay Frères creations include the Oyster, Jubilee, President bracelets for Rolex and the integrated bracelets for both the Audemars Piguet Royal Oak and Patek Philippe Nautilus. Gay Frères was acquired by Rolex in 1998 and ceases to exist as a separate entity in any way.

A bracelet made by the renowned bracelet manufacturer Gay Frères. Also see 'Gay Frères'.

Greenwich Civil Time. A civilian time standard (as opposed to an astronomical one) based on the mean solar time at the Greenwich Observatory, reckoned from midnight as opposed to astronomical time - sometimes represented by GMT - which is reckoned from noon. Thus, 00:00 would be midnight in GCT but midday in GMT. The terms GMT and GCT have different meanings depending on era and place - the distinction between the two was clearer in the United States than in the United Kingdom. GCT was out of use by the 1950s and replaced by GMT that was reckoned from midnight, sometimes called Universal Time (UT) to distinguish it from the original GMT reckoned from noon. Today, GCT is totally obsolete while GMT is understood as a time standard and timezone reckoning from midnight, either as a name for one particular timezone in UTC (Universal Coordinated Time) or as a casual and familiar synonym for UTC.

A style and genre of pocket watch produced for the United States military in the 1940s, featuring a black dial with white markings, coin-edge reeded bezel, nickel-plated case, 24 Arabic numeral hour markers, a prominent outer minute track with Arabic numeral five-minute markers, white spade-and-syringe hands, and a prominent white central seconds hand capable of hacking. The watches usually featured ‘G.C.T.’ as the sole dial text as these watches were meant to be set to GCT which at the time had a similar role to today’s GMT or UTC as a reference time standard. The most famous GCT watch was the Hamilton GCT equipped with a 4992B movement.

A gear is a toothed wheel that rotates to transfer energy in a movement. In watchmaking, smaller gears are called pinions and larger gears are called wheels.

The shape of a gear tooth, specifically the outline from the tip of the tooth to the root on one side of the tooth cross section. Technically each tooth has two profiles, which are usually symmetrical but sometimes asymmetrical. The profile determines various mechanical properties of the gear. In industry at large, the two major profiles are involute and cycloid profiles, with involute being the more modern and widely-used profile. Cycloid profile teeth are vestigially retained in watchmaking. Watchmaking also employs a great variety of profiles for functional and decorative purposes.

A style of indices/markers in the form of a rectangle. Somewhat used interchangeably with ‘baton markers’.

A mechanism that translates constant rotational movement into intermittent rotational movement. The mechanism is composed of two wheels: the driving wheel which constantly rotates and the driven wheel which intermittently rotates. The drive wheel is composed of a wheel with a single pin at its periphery and a small gibbous moon-shaped secondary disk on top of it. The disk meshes with the shape of the driven wheel to keep it in place when not in motion while the pin rotates until it meshes with a slot in the driven wheel. The pin enters the slot of the driven wheel and advances it as the driving wheel rotates. Because the driven wheel only moves when the lone pin makes contact, constant rotational movement is successfully transformed to intermittent movement. The mechanism is also called the ‘Maltese cross mechanism’ as the driven wheel often resembles a Maltese cross. In watchmaking, the Geneve drive is mostly used as a stopwork. See ‘Geneva stopwork’.

A stopwork that utilizes the mechanical principles of the Geneva drive. A driving wheel is mounted coaxially with the barrel to the mainspring arbor so that it rotates as the mainspring winds and unwinds. This driving wheel has a single protrusion (finger) which comes around every rotation of the barrel and meshes with a slot on the driven wheel. The driven wheel typically has only five slots and five arms. One of the arms is significantly bigger than the others and prevents the finger from rotating free of its slot once it meshes. This prevents the barrel from being overwound as it limits the number of rotations a barrel can perform. A side-effect of this is that it also prevents the barrel from completely unwinding, as the stopwork works both ways. While this does keep the barrel within its optimal torque region, it may inconvenience the wearer by having the watch stop prematurely if its power reserve is not replenished. Also see ‘Maltese cross mechanism’.

See 'striping'. The city of Geneva is most closely associated with the technique, so any striping may be called Geneva striping regardless of where the watch is from.

A type of leather. Genuine leather is constructed of leftover leather scraps. It gets its name from how it is the minimum grade of leather that can still be considered leather.

(1926-2011) A watchmaker from London, England and based in the Isle of Man.

An alloy used in the manufacture of watches. Also called 'nickel silver', 'maillechort', or 'Argentan'. German silver is predominantly copper mixed with a white metal such as nickel and/or zinc. It does not contain any silver. German silver was first manufactured by 18th century German metallurgists who were trying to imitate paktong, an alloy smelted directly from the ore. In watchmaking, German silver is most famous for being machined into bridges and plates of movements.

In watchmaking, 'GF' could be an acronym for independent watchmaker Greubel Forsey or bracelet manufacturer Gay Frères.

A bezel that has faded due to wear and time. Especially describes black bezels that have faded to a light gray.

A general term for a dial with contrasting metallic features, especially gold or gold-colored features against a black dial. In the most precise sense, a gilt dial is one of a brass or gold leaf substrate that is exposed through additional layers of galvanically-applied paint - usually black - until the entire dial is finished with lacquer coating to prevent oxidation of the exposed substrate. The desired parts of the substrate are left uncovered by paint through selectively applied transparent coating which prevents the paint from binding with the substrate. They may also be revealed by etching the paint off. To separate this somewhat antiquated but appreciated process from other techniques that produce similar aesthetics, these dials are called 'galvanized gilt dials'. In modern times it is more common to apply gold-colored paint.

A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1791. Abbreviated ‘GP’. Girard Perregaux is owned by the Kering Group.

A nickname for the Seiko reference 7A28-7000 and its reissue, reference SCED035. The watch was one of several Seikos designed by Italian design icon Giorgetto Giugiaro and certainly the most famous in part due to its appearance on the protagonist's wrist in the 1986 film Aliens. Also see 'Ripley'.

Another name for ‘sword hands’. This name was used mostly by Enicar.

See ‘sword hands’.

A watch manufacturer established in Glashütte, Germany in 1994 with claimed roots to 1845. Abbreviated ‘GO’ and alternatively written ‘Glashuette Original’ to render the umlaut in the English alphabet. Glashütte Original is owned by the Swatch Group.

See 'striping'. Used to describe striping done on German watches, especially those made in the Saxon town of Glashütte.

A quick adjustment extension system mounted onto certain Rolex Oyster bracelets. Glidelock allows the anchor of the bracelet to ‘glide’ across the length of the clasp when pushed. This allows for adjustment up to 20mm in 2mm increments. Glidelocks fitted to heavy duty divers like the Deep-Sea have an additional feature which allows for adjustment while on the wrist. While Glidelock makes the clasp larger than those with the more conventional Easylink system, it is a useful feature for dive watches.

The mean solar time at 0 degrees longitude, the Prime Meridian, measured by the Royal Observatory in Greenwich, England. GMT was historically the world’s first global time standard and was measured from midnight for civil purposes and midday for astronomical purposes. Today, it has been largely replaced by Coordinated Universal Time (UTC) for official use as a civil time standard and UT1 as a measure of Earth’s rotation. Nonetheless GMT is closely aligned with UTC and UT1. The three terms are interchangeable in casual conversation.

A complication that displays another timezone with a 24-hour hand, called the 'GMT hand'. On rare occasions the movement may have a 12-hour GMT hand accompanied by a day/night or am/pm indicator instead of the much more common 24-hour hand. The GMT complication requires some sort of independently adjustable hour hand, be it the GMT hand itself, the regular hour hand, or both. Depending on which one is adjustable a GMT complication or a watch with such a complication may either be called a 'caller GMT' or a 'traveler GMT'. In addition to the extra hand, GMT complications almost always feature a date window and frequently feature a GMT/dual time bezel. The GMT complication is identical to the 'UTC complication' and has some mild overlap with the 'dual time complication'.

A hand that displays the time of another time zone in a GMT complication. The vast majority of GMT hands are 24-hour hands, but some exceptions with a 12-hour rotation cycle do exist. The latter must be complemented by a day/night or am/pm indicator which informs the wearer which half of the day the GMT hand is on. Most GMT hands are centrally mounted on the center stack but some have their own subdials.

The part of a sundial that casts a shadow.

A watch collecting social media meme originating from Dutch watch dealer Nico Leonard’s YouTube videos where he consistently exalts the superior attributes and affordable price of Casio watches.

A style of bracelet consisting of flat H-links connected by small center links, each resembling three parallel rice grains. Manufactured by Cartier for the Santos. The name ‘Godron’ is French for ‘gadrooning’, and likely refers to how the center links resemble the convex curves created by the gadrooning technique. The bracelet is rare compared to the default rivet bracelet for the Santos.

A mechanism that transfers energy from the power source of the watch - the mainspring - to the parts that need to move such as the hands. It is a wheel train that primarily consists of the first, second, third, and fourth wheels.

An element often used in the manufacture of watches. Abbreviated Au. Gold is one of the most important metals in watchmaking and is used for crafting virtually any part of the watch including the case, indices, bracelet, hands, and movement. In watchmaking gold is rarely used on its own and rather incorporated into an alloy. Common alloys include yellow gold, red gold, pink gold, white gold, and rose gold. The purity of gold is measured in karats.

A metal is gold-capped when a base layer is capped or fitted with a gold shell. Cap gold is at least 200 microns thick and is generally the thickest gold layer available short of solid gold. While cap gold can look exactly like gold from the dial-side, they almost always have stainless steel casebacks.

A metal is gold-filled when a base layer is mechanically bonded with an outer layer of gold. Gold-filled watches contain far more gold than gold-plated watches, with gold occupying at least 5% of the metal's total weight. The gold layer is usually about 100 microns (0.1mm) thick.

A metal is gold-plated when a base layer is chemically or electrically plated with a thin outer layer of gold. The gold layer is between 0.5 to 20 microns thick and will come off and expose the base metal with time. However, gold-plating is a relatively simple and affordable process that can be redone easily.

A famous charcuterie knife (erroneously known as a cheese knife) which renowned collector John Goldberger used to open the casebacks of a Rolex reference 4113 split-seconds chronograph and an Italian Air Force Universal Genève reference 22560 to reveal their Valjoux 55 VBR movements. This event was witnessed by a great portion of the watch community as it was during an episode of Talking Watches, a popular series by New York-based watch media company Hodinkee. The nonchalant finesse with which Goldberger grabbed the nearby knife, scraped it clean on the sleeve of his tweed jacket, and pried open two priceless timepieces has become something of a legend in the watch community.

Military timezone name for UTC-7.

See 'gong spring'.

A rectangular block of metal that holds the gong spring and fastens it to the case. Also called a gong foot.

Also simply called the 'gong'. A thin strip spring that makes a noise when struck with a striker in a striking complication. The spring is typically mounted to the periphery of the movement. A movement may have more than one gong spring depending on the number of pitches it must make. If there are two gong springs they are typically tuned to bass and treble, with the lower sounds representing a larger unit of time (e.g. hours) and the higher sounds representing a smaller unit (e.g. minutes).

In a striking watch, the governor manages the tempo of the strikes. This is done by regulating the unwinding speed of the repeater mainspring.

See 'grail watch'.

A watch that one would purchase if money were no object. The name is a reference to the Holy Grail, a legendary treasure from Arthurian legend.

The composition, texture, and appearance of an animal hide. Grain may also refer to the grain layer of an animal hide, which refers to the papillary portion. As such, cuts from the reticular layer are not referred to as naturally having grain.

See 'beads-of-rice bracelet'.

A set of design principles established by Japanese designer/engineer Tanaka Taro for Seiko watches of the 1960s. They were designed to add a common, identifiable look to Seiko watches and emphasized sharp edges, high polishes, and flat surfaces. Not all watches of the era adhered to the Grammar of Design.

A watch that has many complications including at least one high complication may be considered a grand complication. Some people regard a grand complication to be a watch that has a perpetual calendar, split-seconds chronograph, and minute repeater. The term is not clearly defined.

(French) 'Great fire'. An alternative term for vitreous enamel. In most use cases, grand feu denotes a dial completely covered in a vitreous enamel coating and embellished with no other enameling technique like cloisonné, champlevé, and flinqué.

A watch manufacturer established in Nagano, Japan in 1960 and now headquartered in Tokyo, Japan. Abbreviated ‘GS’. Grand Seiko is owned by the Seiko Group.

(French) 'Big strike'. A strike sequence that chimes the hour and quarters since the hour every quarter in passing. In other words a grand sonnerie announces the current hour every time it announces the quarters, while the petite sonnerie foregoes the hour strike for every quarter except for each full hour. In modern times many watches are capable of switching between grand and petite sonneries.

(French) Large size. Typically refers to a larger size offering of a certain watch. This nomenclature is most commonly associated with the Jaeger-LeCoultre Reverso.

See ‘longcase clock’.

A tool used for engraving.

See ‘first wheel’.

A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 1665 with only white dial text as opposed to a combination of red and white.

A dial with grooves running horizontally and vertically, sometimes in a globular fashion. The name derives from its resemblance to the grooves and knobs on the surface of a fragmentation grenade. A grenade dial is similar to an embossed grid dial also known as a tapisserie dial, but the knobs on a grenade are significantly bigger and often rounded at the edges. In some watches like the Patek Philippe Aquanaut, the grooves are globular and closely resemble the shape of the iconic Mk 2 fragmentation grenade. Also see 'embossed checkered dial' and 'tapisserie dial'.

A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 2004. Abbreviated ‘GF’. Greubel Forsey is privately owned.

A watch manufacturer established in Oldenzaal, Netherlands in 2008. Grönefeld is privately owned.

Get-together. See 'meetup'.

A sharp dart attached to the swallowtail of the pallet fork. The guard dart is designed to engage with the edges of the passing hollow of a roller in the event of a hard knock or shock that could throw the escapement off proper alignment and cause overbanking. Under normal operation, the guard dart does not touch any other component and merely passes through the passing hollow.

(French) In watchmaking, guillochage is finishing technique that uses engine-turning to mechanically engrave (as opposed to hand-engrave) patterns - typically radial, repetitive, and intersecting - onto a surface. See ‘engine-turning’. In the Anglosphere, guillochage is more commonly referred to as ‘guilloché’ or ‘guilloche’, which in French refers to an engine-turned workpiece, i.e. the finished product of guillochage.

(French) A workpiece whose surface has been finished by guillochage. Also spelled ‘guilloche’. In the Anglosphere, ‘guilloche’ is often used to refer to the technique itself as well. See ‘guillochage’ and ‘engine-turning’.

(French) A decorative technique where repetitive geometric patterns are engraved onto a surface using a rose engine via engine turning.

(French) An artisan who performs guillochage.

Glace, Verte. Rolex nomenclature for a green sapphire crystal.

A two-link bracelet with a stack of H-shaped links interspersed by small rectangular links.

A watch manufacturer established in Saint Petersburg, Russia in 1828 and now headquartered in Schaffhausen, Switzerland. H. Moser & Cie. is privately owned.

A watch manufacturer established in Völkermarkt, Austria in 2004. Habring^2 is privately owned.

An antiquated term for a watch with hacking seconds. Specifically it refers to pocket watches carried around on a maritime vessel as portable timepiece synced to the not-so-portable marine chronometer. In the post-WWII era the term referred to several military-issued wristwatches with a hacking mechanism. Today, the universal proliferation of the hacking mechanism has antiquated the term.

The act of stopping the seconds hand with the pull of the crown. A hacking function allows the wearer to stop the seconds hand when it is exactly at 0 seconds (twelve o'clock) where it can be more accurately set to a more accurate timepiece. While ubiquitous today, hacking was an important feature that was added to timepieces that needed to be extra accurate. It was relatively common in timepieces delivered to the armed forces, maritime vessels, and railways. Also see 'stop/hacking seconds' and 'hack watch'.

Also known as a balance spring. A spiral or helical torsion spring that allows the balance wheel to oscillate at a consistent frequency. The hairspring starts at the collet and terminates at the stud. The hairspring is as thin as a hair, hence the name. Not to be confused with 'mainspring'.

A case with a hinged dial cover that has a transparent window in the middle. This allows the wearer to read the time without opening the cover. The name comes from the half hunter style of pocket watch which featured these covers. Somewhat common in pocket watches, they are rare in wristwatches but not unheard of. Also see 'hunter case'.

A hinged caseback that has an exhibition window in the middle of the cover. The name comes from the half hunter style of pocket watches that had a hinged front cover with an exhibition window that allowed the wearer to read the time without opening it. While half hunter cases on wristwatches is rare but certainly extant, half hunter casebacks are virtually unheard of even though they are technically possible. Also see 'hinged caseback', 'hunter caseback', 'hunter case', and 'half hunter case'

A striking complication that repeats (chimes) the hours and every half quarter (seven and a half minutes) that has elapsed since the last hour. Typically the hours are sounded with a bass note and the half-quarters with a treble note or one of each.

An official mark struck on a metal surface to certify an attribute of the object. While a hallmark may be any kind of such mark, in the narrowest sense it refers to a mark that attests the purity of a precious metal. Hallmarks differ according to period, country or region of manufacture, and other factors and can thus serve as valuable signifiers of the authenticity of a watch.

A watch manufacturer established in Lancaster, USA in 1892 and now headquartered in Biel/Bienne, Switzerland. Hamilton is owned by the Swatch Group.

A percussion device that strikes a gong-spring in a striking watch. A hammer is usually shaped like an axe.

A component of a chronograph mechanism which strikes the reset cam in order to reset the chronograph back to zero. The hammer is usually an axe or club-shaped heel at the end of the reset lever.

A component of a chronograph mechanism which applies constant pressure to the reset lever.

A beak mounted onto a pivot which activates the hammer. As the direct input for the hammer, the trip interacts with the teeth on the bottom of a rack and actuates the hammer once for every tooth that passes through it.

A nickname for Hamilton watches.

A movement which must be wound manually. Synonymous with 'manually-wound' and 'manual wind'. For the vast majority of cases, refers to a type of mechanical movement although there are some exceptions like manually-wound hybrid movements. Also called simply a 'mechanical movement' by some although this term can be technically erroneous and potentially confusing.

The moving components of a clock that displays information by pointing.

The complete set of hands on a single clock regardless of function. Usually of a consistent style.

The stack of hands that are mounted on top of each other.

A watch manufacturer established in Diessenhofen, Switzerland in 1882. Despite still being headquartered in Diessenhofen the company manufactures in Schwenningen, Germany. Hanhart is privately owned.

A form of watch storage designed for maximum protection of the stored goods from impact, abrasion, water, dust, and humidity. The external shell is usually hard plastic and/or rubber and the interior is typically lined with thick and soft foam padding. Unlike most watch cases and boxes which are designed stylishly, hard cases are utilitarian. They typically come with aggressive ribs and buttresses to absorb impact and have large carry handles. Many come with internal locks or holes for padlocks.

(French) High horology. A term that describes watchmaking as an art form as opposed to more practical or pedestrian watchmaking. While there is no clear definition or boundary, the term usually refers to timepieces crafted with exquisite materials, lavish embellishments, and/or complicated mechanics by master craftsmen. Generally, a watch that is simply expensive or rare is not considered haute horlogerie if it does not possess the aforementioned characteristics.

A macaronic Franglais term that is in between the French term 'haute horlogerie' and its corresponding English term 'high horology'.

In a chronograph, ‘heart piece cam’ can either refer to the reset cam which resembles a human heart or the cam that serves as the control system in a cam chronograph. The former use is far more common.

A name used by Elgin to denote the extra-bold sans-serif Arabic numeral font more commonly called ‘Box Car numerals’. See ‘Box Car numerals’.

A name used by Hamilton to denote the extra-bold sans-serif Arabic numeral font more commonly called ‘box car numerals’. See ‘Box Car numerals’.

The perpendicular length of the watch from a flat surface. It is also commonly called the 'thickness'. Height mostly refers to the case height, which measures from the caseback to the bezel, excluding any protruding crystal. If the height of the crystal is included in the measurement it is usually mentioned.

A one-way valve that allows pressurized helium atoms to escape the case of a dive watch so that the accumulated pressure inside the watch does not blow out the crystal when the diver resurfaces. Dive watches are generally impervious to water but cannot stop helium as it is the smallest atom on the periodic table. Helium is heavily used by saturation divers in their mixed breathing gases which help them reduce the risk of nitrogen narcosis in deep dives or long stays underwater. An HEV redirects the helium out of the watch while still keeping larger particles such as water molecules out so that there is no accumulation of pressurized helium in the watch that may cause an explosion when there is no longer equivalent water pressure pushing down on the crystal. While not really an essential feature on deep divers, HEVs have become loved by marketing departments.

A nickname for dive watches with a water resistance of 666ft (202m). The name comes from the ‘number of the beast’ or the ‘devil’s number’. Several dive watches from the 1960s and 1970s had this water resistance including those made by Bulova and Caravelle. 666m is much less common, but it would still qualify as a hell diver.

A nickname for the Seiko 6139-710X series automatic chronographs that have bulky cases that somewhat resemble the so-called coal scuttle profile of the WWII-era German Stahlhelm. The black variant of the Helmet chronograph is also called the 'Darth Vader'. In Japan, the Helmet is called the 'Fujitsubo', a name it shares with the so-called 'Tokei Zara'.

Omega's brand of acrylic watch crystal.

(French) Jumping hours.

Any clasp that is hidden from view. Usually a single or double-fold clasp, the hidden clasp is usually found on bracelets but also rarely on straps. Hidden clasps contribute to a sleek design and also may provide for a less bulky and more comfortable wearing experience. A hidden clasp's location may be subtly hinted by the existence of push buttons at the sides, a latch or button on the bracelet, or nothing at all.

A style of lugs that are completely obscured from the top view. This style usually comes in the form of a cutout for the strap ends on caseback-side. Hidden lugs can also include some varieties of shrouded/hooded lugs.

A horological complication that is difficult to make. The term does not have clear boundaries. However, complications that are universally regarded as high complications include the perpetual calendar, minute repeater, and tourbillon. Extremely rare and complex complications may also be regarded as high complications.

A term that describes watchmaking as an art form as opposed to more practical or pedestrian watchmaking. A direct translation of the French term 'haute horlogerie' which is also commonly borrowed into English as is or as the Franglais term 'haute horology'. While there is no clear definition or boundary, the term usually refers to timepieces crafted with exquisite materials, lavish embellishments, and/or complicated mechanics by master craftsmen. Generally, a watch that is simply expensive or rare is not considered high horology if it does not possess the aforementioned characteristics.

A caseback that has a hinged cover that allows it to be opened. A hinged caseback would have two components: the hinged cover and the caseback itself. Hinged casebacks originate from small pocket or pendant watches that were converted into wristwatches during the incipiency of the wristwatch. Hinged casebacks come as standard on most pocket watches but is considered a novelty feature on modern wristwatches. They often reveal a display caseback under the cover, which offers the benefits of both a solid and display caseback. Also see 'officer caseback', 'hinged dust cover', 'hunter caseback', and 'half hunter caseback'.

A dial-side cover mounted on a hinge that allows it to be opened. In pocket watches with open faces, i.e. with no transparent crystal, the hinged cover allowed the owner to read the time when needed and keep the case closed when the watch was stored away. Today, cases with these covers are known far better as hunter cases. Also see 'hunter case' and 'savonnette'.

An alternative name for a hinged caseback. Used by Patek Philippe. The name originates from how the hinged cover on pocket watches would prevent dust and foreign materials from entering the holes for the winding key on older pocket watches. Before the adoption of crowns, pocket watches had to be would and set by inserting a key into a hole in the caseback. The hinged dust cover was a necessary solution to this. Also see 'hinged caseback', 'hunter caseback', 'officer caseback', and 'half hunter caseback'.

In watchmaking, a hobnail finish or hobnail pattern is a guilloché/engine-turning finish where the surface of the workpiece is covered in a grid of square pyramids - pyramids with a square base. The purpose is purely decorative and is typically featured on the bezel. The technique is also called ‘clous de Paris’ or ‘Paris nails’. Hobnail finishes should not be confused with diamond knurling, a finishing technique that produces a somewhat similar result. Hobnail patterns are composed of square pyramids while diamond knurling yields pyramids with a rhombus base. Also see ‘knurling’. Hobnail patterns in watchmaking should also not be used interchangeably with those in other areas, such as ceramics or jewelry where the term refers to a different finish.

An online watch publication based out of New York City, USA.

An end link that is constructed of hollow, usually stamped metal. Hollow end links may consist of two components which must be assembled to serve as a complete end link. Hollow end links are lighter than solid ones but can be rattly, tinny, and flimsy. They are commonly found on vintage watches and on more affordable modern bracelets. Also see 'solid end link'.

See 'grail watch'. The term may also refer to a watch of an exceeding rare reference or condition.

A nickname for the Omega Speedmaster Automatic reference 376.0822. While the ref.376.0822 is by no means the rarest or most valuable Omega, the nickname comes from the personal journey of renowned collector Chuck Maddox to add the watch to his collection. Maddox’s well-documented and widely-read account of his hunt put his nickname for the watch into mass circulation and has since cemented itself as the standard epithet for the ref.376.0822.

While the name 'Holy Grail' can describe many watches in the vast catalogues of Seiko, it typically refers to the Seiko 5 Sports reference 6138-8010 Speed-timer automatic chronograph. The name comes from the watch's highly-coveted design and rarity.

In watchmaking, the Holy Trinity refers to an unofficial triad of prestigious watch manufacturers deemed to be at the pinnacle of watchmaking, namely Patek Philippe of Geneva, Vacheron Constantin of Geneva, and Audemars Piguet of Le Brassus. In reality most horologists and enthusiasts do not take this term seriously.

A clock, usually a watch, which heavily references if not outright copies the design of another but uses a different brand name. Technically homages are not counterfeits or replicas but have about as much originality.

A nickname for the Tudor Oysterdate reference 7031. The name comes from the shield-shaped hour markers which resemble baseball home plates.

The time where one's home is, or one's reference timezone.

A style of lugs where the space between the lugs is obscured with some sort of metal cover, either fixed or articulating. Also known as ‘shrouded lugs’. Hooded lugs can overlap with hidden lugs, especially the variants where the lugs, not only the space between, are also covered by an extension of the case.

As the extension, so the force (Latin: ut tensio, sic vis). An empirical law which states that the force needed to extend or compress a spring by a certain distance is linearly proportional to the distance. In watchmaking where the important springs in question are spiral spring, this law can be applied to state that the torque exerted by the mainspring is linearly proportional to its angle of rotation. This is important because mainsprings do not always follow Hooke’s law. When the mainspring is fully wound, it cannot absorb any more energy so excess turning force from winding the stem goes elsewhere. When the mainspring is nearly fully unwound, the spring pushes outward agains the inner barrel wall and exerts disproportionately low torque. Keeping the mainspring operating within its optimal range where it follows Hooke’s law is key to enhancing the accuracy of a timepiece as the torque output determines the speed of the movement.

(French) A watch or clock.

A style of lugs that resemble animal horns. They are bulbous at the base and come to a sharp tip, usually with a curve. The most famous of these would likely be the ‘cornes de vache’ or cow horn lugs. See ‘cornes de vache’.

A person who studies horology. Also a fancy term for a watch enthusiast. In the past, horologists studied time itself, timekeeping, and manufactured timekeeping devices. Today the three disciplines are usually separate.

The study of timekeeping devices. While the term literally means 'the study of time', horology focuses more on the human measurement of time rather than the properties of time itself. In the modern context, horology refers broadly to the study of timekeeping instruments. The similar term 'chronometry' refers to the science of timekeeping and its standards. The watch collecting hobby is more appropriately placed within the realms of horology as it concerns timekeeping devices more than time itself. However, there is significant overlap and neither horology nor chronometry is complete without the other.

Military timezone name for UTC-8.

The hand that points to the hour. Usually makes a full rotation every twelve hours, with the exception of a few watches with 24 hour displays.

Visual (sometimes tactile) indications of the hours in various forms, including numerals or shapes, and in various techniques including painted, printed, engraved, carved, and machined and applied. Most watches have twelve hour markers while a minority have twenty-four. Also called ‘indexes’ or ‘indices’, both acceptable plural forms of ‘index’.

A rack which interacts with the hour snail and the hammer trip of the bass hammer. It is lined with twelve teeth, one for each hour of the dial.

A component of a chronograph which moves the chronograph hour hand.

A snail cam which transmits information on the current hours to the hour feeler so that a repeater can announce the current hours. The hour snail is in the shape of a logarithmic spiral with four steps.

A component of the motion work that rotates the hour hand. The hour wheel consists of a wheel and a pipe, the latter of which mounts the hour hand. The wheel meshes with the minute wheel pinion and turns once every twelve hours. The hour wheel sits on the top of the shaft of the cannon pinion and is the directly under the dial. It is separated from the dial via a dial washer.

A gemstone and borate mineral of a generally white and milky hue with web-like gray veins. For this reason it is often mistaken for white marble. In watchmaking, howlite is typically used to make rare stone dials. They are often called ‘marble dials’.

A watch manufacturer established in Geneva, Switzerland in 1980 and now headquartered in Nyon, Switzerland. Hublot is owned by LVMH Moët Hennessy Louis Vuitton.

A nickname for the Rolex Oyster Perpetual Submariner reference 116610LV, a Submariner with a green dial and green ceramic bezel insert. The name is a reference to the green color of the dial and bezel.

An alternative name for a hinged dial cover. A case with a cover on the dial-side. This protects an open-face watch from breakage, which is no longer a concern today with sapphire crystals. Today the cover serves an aesthetic or stylistic purpose. The name comes from the hunter style of pocket watch which commonly featured these covers. Very common in pocket watches, they are very rare in wristwatches but not unheard of. See 'hunter watch', 'savonnette', 'half hunter case', and 'hinged dial cover'.

An alternative name for a hinged caseback. The name 'hunter' comes from the hunter style of pocket watches, which featured a spring-loaded hinged cover. Technically, the term 'hunter caseback' is not fully accurate as the hunter watches featured their iconic covers on the dial-side, with the movement-side having the usual hinged caseback. See 'hinged caseback', 'half hunter caseback', 'hinged dust cover', and 'hunter case'.

A pocket watch that features a hinged front cover and savonnette movement. These watches were marketed as hunter watches in America, which prompted manufacturers to engrave elaborate hunting scenes on the case. Also see 'savonnette'.

One of the three major types of movements. A movement which combines some components of mechanical movements and some components of electronic movements. Examples include electric movements which use an electric battery to power a mechanical balance or a tuning fork, or Seiko's Spring Drive movements which use a mechanical gear train to power an electronic integrated circuit which keeps time and an electromagnetic brake which regulates the movement.

An element that is sometimes used as the frequency reference in atomic clocks. They are more specifically known as hydrogen maser clocks.

A watch manufacturer established in Neuchâtel, Switzerland in 2012. HYT is owned by Kairos Technology Switzerland.

A unit of frequency that measures actions per second. One noteworthy point is in a mechanical movement, an oscillation is regarded as a single action. Therefore, two semi-oscillations or two beats constitute a single action. This means that when converting bps or vps to Hz, the value is halved. For example, a watch that ticks ten times per second runs at 10 bps or 10 vps. However, in Hertz, it runs at 4 Hz. Meanwhile, this is not the case for a quartz movement. A quartz movement that vibrates at 32,768 vps is in fact vibrating at 32,768 Hz.

A colloquial term for diamonds.

A dial with a metallic light blue color. In Rolex watches, the ice-blue dial means that the watch is made of platinum.

A colloquial term for a watch that has been set with diamonds.

(French) Waterproof. See 'waterproof'.

The surfaces of an escape wheel tooth and pallet jewel which come into contact with each other during the impulse of the escapement.

A component of the balance that strikes the pallet fork horns. The function of the impulse jewel is to relay impulses from the pallet fork to the balance which allows the balance to operate, and to strike the pallet fork at the frequency that the balance swings which allows the pallet fork to seize and release the escape wheel at the speed dictated by the balance. It is a small semi-cylindrical jewel (typically a ruby) that protrudes from the impulse roller. It is also known as a ‘roller jewel’, ‘impulse pin’, ‘impulse jewel’, and ‘cheville’.

See ‘impulse jewel’.

The main roller, particularly in the context of a double roller escapement where differentiation in terminology from the smaller safety roller is necessary.

In a striking watch, a strike in passing is activated at certain predetermined times. Antonymous with 'on command'. Examples of strikes in passing are grande and petite sonneries, which chime only at designated times such as each full hour and quarter-hour.

In person. A play on the phrase 'in the flesh'.

Executed internally by the company. The term has no clear standard as to what it means. Thus it is used more liberally by some than others. In-house most commonly refers to the movement which is usually the most difficult and complicated aspect of watchmaking and therefore commonly outsourced. However the term can refer to absolutely anything. Antonymous with 'outsourced'.

A movement both developed and produced internally by the watch manufacturer. As it is virtually impossible for any company to produce absolutely all the parts needed for a watch movement, the term does not have an exact standard. Most in-house movements are designed in-house and manufactured almost entirely in-house, while using some readymade components. Some self-described 'in-house' movements are based on ébauches but are so heavily modified that they are unrecognizable. What makes a true in-house movement is the subject of debate. See 'proprietary movement' for a similar term, 'ébauche' for an opposite term, and 'third party movement' for a related term.

A style of display where the assets are arranged in a single line. Typically used for mechanical perpetual calendars where the in-line arrangement requires a high degree of mechanical complexity.

An independent watch manufacturer that is not a part of a parent company. While independents come in many shapes and sizes, many independents revolve around a single master watchmaker or a small team of them with a concentrated vision and a focus on horological engineering. Therefore, companies like Patek Philippe which are not owned by anyone else but are still corporate in structure are not considered independents. Very small scale brands that focus more on factors other than movement engineering are called 'microbrands' and are referred to more commonly as such. Therefore, to describe a company as 'independent' is different from describing it as 'an independent'.

A hand - usually an hour hand - that can be adjusted without resetting the watch. Normally one must pull out the crown to its setting position to move any of the hands. Independently adjustable hands can be set at a dedicated crown position or with a pusher or corrector. This feature is commonly seen in watches that can display multiple timezones.

A marking on a dial which indicates the hours. Synonymous with 'hour marker'. 'Indexes' and 'indices' are both acceptable plural forms of index. Indices can be numerals, but the term usually refers specifically the geometric shapes such as sticks, rectangles, circles, and others that are used in lieu of numbers.

A lever that adjusts or serves as a visual reference for the regulator.

See ‘baton hands’.

Military timezone name for UTC-9.

A term denoting microbrands, some independent manufacturers, and other smaller watch manufacturers. While the term 'indie' normally means 'independent', the word is used to refer to a slightly larger group of watch brands than 'independent'. As with many of these conceptual terms, the terminology is not clear-cut.

An arrangement of center seconds where the fourth wheel is not at the center of the movement and thus requires gearing that connects the fourth wheel to a wheel at the center which drives the seconds hand. Indirect center seconds maintains the conventional and traditional layout of a mechanical movement but makes the movement thicker due to the additional gearing and hinders precision, especially because of the addition of a tension spring to ensure the seconds hand moves normally despite being far and away from the power source that is the mainspring. Indirect center seconds can usually be identified with an extra bridge on top of the movement to hold the extra gearing, but is no longer common due to the proliferation of the mechanically superior direct center seconds.

A disc-shaped weight that can be added or removed from the inner rim of a cam-poised/inertia/masselotte balance wheel to adjust the amplitude of the wheel. Also called by its French name 'masselotte'.

A bracelet that is built into the watch head and is not designed to be removable. Integrated bracelets are distinguished by an absence of lugs or the use of extremely proprietary lugs that would only fit the intended bracelet. Like most watch parts, even an integrated bracelet is technically removable and replaceable with a custom-made alternative or authentic parts. However the process would be exceedingly more difficult than with a conventional watch which uses spring bars, conventional lugs, and band. Also see 'integrated strap'.

A chronograph mechanism that is designed as a native part of a movement as opposed to a separate mechanism that can be attached to a movement. Antonymous with ‘modular chronograph’. Integrated chronographs can be more difficult to design as the inherent complexity of chronographs poses obstacles to the design process. However, they often have many technical advantages especially in thinness, architecture, and mechanics. Integrated chronographs often have a more dispersed architecture which makes for smoother operations and ease of servicing.

A set of electronic circuits placed on a single chip surface made of semiconductor material like silicon. Also known as a chip, IC chip, microchip, and IC. An IC is an essential component on a quartz watch and some hybrid movements. It converts energy (usually from an electrical power source like a battery or capacitor) into pulses which activate the quartz oscillator, and then converts the vibration pulses of the quartz oscillator into a reduced signal for the motor - which moves the hands of an analog watch - or a LCD/LED display. In a way the IC 'counts' the vibrations of the quartz oscillator and makes sure that the seconds hand advances once for every pre-determined number of vibrations. Usually that number is 32,768 vibrations per second.

Lugs that have no clear border with the case. A famous style is cushion lugs.

A strap that is built into the watch head and is not designed to be easily removable. Integrated straps are distinguished by an absence of lugs or the use of extremely proprietary lugs that would only fit the intended strap. Like most watch parts, even an integrated strap is technically removable and replaceable with a custom-made alternative or authentic parts. However the process would be exceedingly more difficult than with a conventional watch which uses spring bars, conventional lugs, and band. Integrated straps are almost always resin or rubber and are much rare than integrated bracelets. Also see 'integrated bracelet'.

A wheel whose sole purpose is to connect two moving components that are far apart and transfer input. Intermediate wheels are common in mechanical movements and can almost always be found in the keyless works. See ‘intermediate wheel (keyless works)’. Intermediate wheels also play a key role in chronographs. See ‘intermediate wheel (chronograph)’.

A component of the keyless works that meshes with the sliding pinion of the crown stem and the minute wheel in order to set the time. The intermediate wheel is normally disconnected from the crown stem because the sliding pinion is retracted unless the crown is pulled to the setting position. Keyless works typically have one or two intermediate wheels.

A component of a chronograph mechanism which receives input from the finger of the chronograph runner (chronograph seconds wheel) and transfers it to the minute recording wheel. As it is mounted on a bridge attached to a sliding lever, it is also known as a ‘sliding wheel’.

A gear tooth profile based on an involute as opposed to a cycloid. An involute of a circle is a spiral that follows the path of a string unraveling from a point on a circle. In simple terms, an involute profile is round and bulbous , with no straight flank. This is in contrast with the relatively straight-sided cycloid profile. Originally an evolution of the cycloid, the involute profile is by far the most dominant profile in industrial gearing thanks to its constant pressure angle, superior longevity, smoothness, and ease of manufacturing. However, the opposite is true in watchmaking where cycloid profiles have clear advantages.

The property of a mechanical oscillator to maintain a constant oscillation period irrespective of oscillation amplitude, or the ability of a mechanical oscillator to maintain a fixed cycle despite variable amplitude. This means that a mechanical oscillator (e.g. a balance, pendulum, etc.) will take the same amount of time to complete an oscillation even if its angle of movement differs for every oscillation. For example, a balance wheel is isochronous if a 210, 215, and 220 degree swing all take 0.1 seconds to complete. Isochronism is central to accuracy as it is essentially a timekeeping organ’s ability to keep consistent time notwithstanding various mainspring power levels, temperatures, shocks, and vibrations which may impact the amplitude of the balance.

A watch that has been issued by an organization of governmental and/or military nature. Militaries, intelligence organizations, and government foreign services often issued watches to their operatives for various reasons throughout history. These watches are often the subject of discussion, adoration, collection, and research in the watch community due to the stories involved, the relative rarity of these pieces, and the fact that issued watches are mostly a thing of the past. Some issued watches have special markings that indicate them as government property or certain modifications to meet military requirements.

A watch manufacturer established in Schaffhausen, Switzerland in 1868. The name stands for 'International Watch Company'. IWC is owned by Richemont.

A nickname for the Patek Philippe reference 2458 in platinum housing movement number 861121, an observatory-certified movement that was trialed in 1948 and one of only two Patek observatory movements ever cased in a wristwatch. The watch takes its nickname from the man it was delivered to, and bears his name on the dial. Joe Ben Champion (1917-1975) was a Texan lawyer who possessed several Patek Philippe creations.

A watch manufacturer established in Le Brassus, Switzerland in 1833. Abbreviated ‘JLC’. Jaeger-LeCoultre is owned by Richemont.

A nickname for the Omega Seamaster reference 2541.80.00 worn by Irish actor Pierce Brosnan as MI6 agent James Bond in the 1995 film GoldenEye.

‘The’ James Bond Omega is the reference 2541.80.00, the first Omega that James Bond ever wore. The watch appeared on the wrist of Irish actor Pierce Brosnan in the 1995 film GoldenEye. Also see ‘Bond (Omega)’.

A nickname for the Rolex Oyster Perpetual Submariner reference 6538, which was worn by Sean Connery as MI6 agent James Bond in the 1962 film Dr. No. This reference is also known as the ‘Big Crown’ due to its oversized crown.

A nickname for the Rolex Oyster Perpetual Deepsea references 116660 and 126660 which accompanied film director James Cameron in his record-breaking descent to the bottom of the Mariana Trench in 2012.

See 'Kanji date wheel'.

A gemstone and variety of silica that has several hues including green, red, yellow, brown, and blue. In watchmaking, jasper is typically used to make rare stone dials.

Japanese Domestic Market. It may also stand for 'Japanese Domestic Model' or 'Japanese Domestic Manufacture'. All three meanings are roughly the same, as the Japanese market almost always gets Japanese-made models from domestic manufacturers anyway. The term is used in the watch world just as it is in the automotive world. JDM watches are sought after by collectors for their purportedly superior quality, special editions, Japan-exclusive models, or relative rarity.

(1720-1814) A horologist from Challex, France and active in Paris. Lépine was the King’s Clockmaker under Louis XV, Louis XVI, and Napoleon Bonaparte. He was a master of Abraham-Louis Breguet. Lépine is most noted for the Lépine caliber which radically thinned movements and made the archetypal pocket watch possible. He is possibly the first to employ bridges in clockwork architecture. Some other of his numerous contributions include keyless works, toothed mainspring barrel, deadbeat seconds, and improvements on repetition and moon phase. His tremendous innovations on watch aesthetics are often misattributed to his protégé.

A nickname for the Rolex Oyster Chronograph reference 6236, and sometimes broadly the entire Rolex 'Dato-Compax' range including references 4768, 4767, 5036, and 6036. The name comes from French alpine ski racer Jean-Claude Killy who allegedly owned a ref.6236. While this is unfounded, the association will likely not disappear.

A nickname for the Omega Seamaster reference 145.0024. The watch was one of the Star Wars triad nicknamed by renowned collector Chuck Maddox alongside the ref.145.023 ‘Anakin Skywalker’ and ref.145.0023 ‘Darth Vader’. The triad share their distinctive large shell and utilize the same cal.861 movement - essentially they are the same watch with small variations in dial composition and case shape. This distinction is important as the Jedi nickname is usually misattributed to the ref.176.0005, a completely different watch with little in common with the ref.145.XXXX series. This was due to a cataloguing error by watch auction house Antiquorum.

In watchmaking, 'jewel' refers to a jewel which is used in a clock movement. Jewels are used as more durable, corrosion-resistant, temperature-stable, and lightweight alternatives to metal for surfaces or components where high levels of constant friction are expected. These jewels are usually synthetic but may occasionally be natural. Most jewels are based on corundum. Contrary to certain popular understandings, the jewel count of a movement does not determine how expensive or exquisite it is, though a higher jewel count may hint at a more complex movement. Jewels can be classified by into holed, cap, roller/impulse, and pallet jewels.

A style of crown adorned with a jewel. The jewel serves a purely aesthetic purpose.

Jeweling may refer to a broad range of embellishments on a metal surface, but typically refers to pearling. See ‘pearling’.

A nickname for the Heuer Autavia reference 1163T chronograph. The name comes from Formula One racing driver Jo Siffert, who famously wore the watch. The sponsorship deal between Siffert and Heuer was the first watch sponsorship in F1 history.

A nickname for the Heuer Autavia reference 2446 chronograph. The name comes from Formula One racing driver Jochen Rindt who famously wore the watch. Also see ‘Nina Rindt’ for the Universal Genève chronograph worn by and named after his wife.

(1736-1799) A horologist from Cornwall, England and active in London. Arnold is credited with catalyzing the rapid development of portable timepiece accuracy, popularizing and possibly inventing the word ‘chronometer’, greatly improving the bimetallic compensation balance, inventing the pivoted detent and spring detent escapements, overcoil balance spring, and likely the concept of the tourbillon.

(1693-1776) A horologist from the West Riding of Yorkshire, England and active in London. Harrison is credited with the invention of the marine chronometer which was a crucial device in the projection of British military and commercial power across the seas. He also invented the gridiron pendulum and the grasshopper escapement among several other modifications to existing technologies.

A nickname for a variant of the Rolex Cosmograph Daytona references 6239, 6241, and 6264 'Paul Newman' in yellow gold with a black dial and gold sub-registers. The name 'John Player Special' is a reference to the tobacco company, whose black-and-gold livery adorned the Lotus 76, 77, 78, and 79 Formula One cars.

See 'John Player Special'.

A five-link bracelet with narrow and short semicylindrical links and single-fold clasp produced by Rolex. The original bracelets were made for Rolex by Gay Frères. The Jubilee bracelet comes with a wide range of models including the Datejust, GMT-Master II, and Sky-Dweller. Due to its iconic status the bracelet has been widely mimicked and copied.

Military timezone name for local time. Any timezone where the observer is currently located can be denoted ‘Juliet time’ or ‘J’, e.g. 0630J.

The larger variant of a watch. The term may also refer to an 'oversize(d) watch'.

A nickname for the Omega reference 2505 and other similar 38mm watches made by the company in the 1940s and 1950s. The name comes from the watch’s large size compared to its contemporaries, as the average men’s wristwatch was usually no larger than 35mm at the time.

A nickname for the Seiko 6138-300X series chronographs which have large dials and cases.

The act of moving instantaneously as opposed to continuously.

A type of component that consists of a flat spring that applies force to another component to keep it in place, restrict its movement until deliberately actuated, or control the speed of movement. Jumpers can be frequently seen applying force to wheels, levers, and yokes and are used commonly in mechanical movements.

A mechanism and display style of the hours where the hours are digitally represented and ‘jump’, or instantaneously change. Due to the ambiguity of the term ‘jump’, the term may also refer to an analog hour hand that is designed to jump ahead once every hour as opposed to continuously moving. The latter use is incredibly rare.

A nickname for the Rolex Oyster Perpetual Day-Date reference 18238 fitted with a fossil dial created from a thin slice of fossilized stone. The dial had a pattern somewhat resembling the glassmaking technique of millefiori. The Jurassic Park was offered in two shades.

(Japanese) A nickname for the Seiko 6138-003X series automatic chronographs. The name means 'square eyes' in Japanese, a reference to the square sub-registers.

A nickname for the Tensoku watches worn by Japanese pilots during the Second World War. There is no direct relation between Tensoku watches and kamikaze attacks, even though it is not unlikely that at least a few were on the wrists of Mitsubishi A6M pilots in suicide attacks. Also see 'Tensoku'.

(German) Combat swimmer (diver). A nickname for the Panerai dive watches supplied to Nazi Germany during the Second World War.

A day wheel with the days of the week written in the Sino-Japanese script Kanji. Synonymous with 'Japanese day wheel'. Kanji wheels typically feature only one distinguishing character but longer apertures may allow for the display of all three characters. They are common in Japanese watches made for the domestic market but are seen as collectible overseas.

A loop that retains a strap. Keepers are used to keep extra strap length tidy and flush to the wrist. Keepers may be fixed or floating, with most straps having one fixed and one floating keeper.

A nickname for the Rolex Oyster Perpetual Submariner reference 16610LV, a special edition of the Submariner celebrating the 50th anniversary of its introduction. The name is a reference to the lime-green color of the stainless steel bezel insert.

A group of mechanisms including the crown and the components it controls. In other words, a group of mechanisms that deals with the setting and/or winding of a clock. Like most curious terms, ‘keyless works’ is a relic of the distant past. Clocks used to be wound and set by a pair of small keys which were inserted into holes in the case that gave access to the movement. The ‘keyless’ works eliminated the need for this by adding a component called the ‘crown’ which could be used to set and wind the clock. Thus, the crown and its associated components which form the winding and setting mechanisms became known as the keyless works.

(Arabic) A J-shaped dagger of Omani origin. In watch collecting nomenclature, a ‘Khanjar’ is the national emblem of Oman or a variation of it that was printed onto the dial, engraved on the caseback, or marked on the documentation and packaging of a watch gifted by Sultan Qaboos bin Said Al Said (r. 1970-2020) of the Sultanate of Oman. The Khanjar came in three different colors, perhaps reflecting the three national colors of the country: white, red, and green. It also came in three styles: the national emblem, a crowned national emblem, and the crest of the Royal Oman Police. Also see ‘Oman dial’ and ‘Qaboos dial’.

A watch designed for children. Typically the watch is designed to teach children how to read analog clocks and familiarize them with time.

Military timezone name for UTC-10.

A watch ordered by the North Korean government during the reign of Kim Il Sung (r. 1948-1994) and bearing his signature. Orders for these watches peaked in the 1970s for the event of Kim's 60th birthday in 1972. The most famous and desirable examples were manufactured by Omega, with Kim's signature taking precedence over the Omega signature. The watches often came with Korean day wheels.

(Japanese) A nickname for Grand Seiko watches with 'kirazuri' dials, including the reference SBGA387. Kirazuri is a finishing technique in Japanese woodblock printing that uses mica powder to add sparkle. The kirazuri dials mimic this effect, but with a textured metal plating over the dial plate instead of mica. The resulting texture is similar to that of a linen dial, but with noticeably more sparkle and variation in density.

See ‘diamond hands’.

A nickname for the Seiko references SKXA47/49/51, SHC053/55, and SMY089 divers. The SKXA series is automatic, SHC quartz, and SMY Kinetic. The etymology of the nickname is unclear.

See ‘overbanking’.

A finishing technique where lines are pressed or cut into a workpiece to create a hatched surface. The lines may run parallel with the workpiece (straight knurling), diagonally one way (helical knurling), or diagonally two ways (diamond knurling). In watchmaking, knurling is the most common as it can make crowns grippier. Diamond knurling may be confused with the hobnail pattern - while the hobnail pattern is a guilloché technique which means that material from the workpiece is cut away by an engine, knurling may be performed either by hand or CNC machine and is not always cut away. Moreover, the visual difference is apparent as hobnail patterns are composed of square pyramids while diamond knurling is composed of much smaller pyramids with rhombus bases, and is typically not as finely executed.

A thin mesh bracelet with a sliding clasp and adjustable straight end. The Komfit bracelet is renowned for its high adjustability thanks to its sliding clasp and compressible straight end link which can accommodate multiple lug widths. Thanks to this adjustability, the bracelet became a popular choice for astronauts in NASA and became an iconic pair with the issued Speedmasters of the era.

A day wheel with the days of the week written in Korean. Quite rare, Korean day wheels were most famously used in watches ordered by the North Korean government.

A rare term for the exit pallet of the pallet fork. Presumably short for ‘left stone’ as the exit pallet is on the left arm of the pallet fork from the balance’s point of view. Also called the ‘discharging stone’.

A marking that indicates that the dial contains photoluminescent paint such as strontium aluminate. This marking is optional as photoluminescent paint is not radioactive and virtually harmless to the human body even after direct exposure.

A resin or wax coating on top of a wooden or metal surface. In watchmaking, lacquer is most commonly found as a dial finish.

A bracelet with short center links and large spaces between them. Sometimes bamboo bracelets are called ladder bracelets, but ladder bracelets usually refer to oyster-style three-link bracelets whose empty spaces' sole purpose is ventilation or style.

See 'women's watch'.

See ‘alpha hands’. In common parlance, lance hands are generally a bit thinner than alpha hands.

A nickname for the Seiko 5 Sports SKZ2XX series expedition watches. The nickname likely comes from the fact that the watch looks like a dive watch but is intended for use on land. It is also known as the 'Atlas'.

A clock style with a box body and a hemispherical bell suspended on the top, resembling a lantern. Lantern clocks were often mounted to walls but there were also variations which utilized pedestals. Later evolutions of the lantern clock which did not use weight-driven movements (which required clearance for the suspended weight and rope/chain) were mounted on footed bases. Lantern clocks also influenced the development of wadokei, or Japanese clocks.

A metamorphic rock of a deep-blue hue, composed primarily of lazurite, calcite, and pyrite. Lapis lazuli was famously used to create deep blue pigments in medieval Europe, as it was the primary ingredient of the highly-valuable ultramarine pigment. In watchmaking, lapis lazuli is a rare but notable material for its use in making the exotic lapis lazuli dial.

A chronograph clutch system that is arranged horizontally. A horizontal clutch is the more conventional and traditional arrangement where the driving wheel, coupling wheel, and chronograph runner (chronograph seconds wheel) are connected horizontally via meshing leaves. Lateral clutches may suffer long term wear due on the teeth. They are also prone to wobbly seconds hand movement upon starting and cause a drop in amplitude which may negatively affect the accuracy of the watch. While technical traits are in favor of the newer vertical clutch system, lateral clutches tend to be thinner. Many enthusiasts prefer the aesthetics of the lateral clutch as well, due to the visibility of the wheels and their meshing.

A machine that rotates a workpiece (a piece of raw material that is getting worked on) on an axis of rotation. The potter's wheel is the most famous type of lathe, but most lathes including those used in watchmaking turn the workpiece on an axis parallel, not perpendicular to the ground. Lathes are ubiquitous tools in watchmaker's workshops as watch dials often have repeating and circular geometric embellishments that require a rotating axis. The rose engine lathe is perhaps the best-known type of lathe in watchmaking due to its ability to produce the desirable guilloché finish.

Lunette Bleue. Rolex nomenclature for a blue bezel.

A style of hands distinguished by a curving taper, reaching maximum width at the midpoint of the hand and then coming to a thin tip. The hands resemble thin leaves. Also called by their French name, ‘feuille’ hands. Leaf hands are rarely lumed.

An intercalary date added periodically to certain years to offset the difference between the nominal length of a year in the human Gregorian calendar and the actual length of a solar year (the orbital period of Earth around the Sun). This takes the form of an extra day added to the end of February, which gains a 29th day in a leap year. Also see ‘leap year’.

An intercalary year containing an extra unit of time to offset the difference between the nominal length of a year in the human Gregorian calendar and the actual length of a solar year (the orbital period of Earth around the Sun). This extra unit is a day, or ‘leap day’ in the Gregorian calendar while the Chinese lunisolar calendar and derived systems have a leap month. In the Gregorian calendar, all years divisible by 4 (e.g. 2004) are leap years, unless the year is centurial and thus divisible by 100 (e.g. 2100). However, if the year is also divisible by 400, it is a leap year (e.g. 2000).

A system of grading the quality of leather. Leather grades are usually determined by tanneries in an alphabetical system. There is no universally agreed standard on leather grades. In the watch world, different cuts and layers of leather used for watch straps are erroneously referred to as grades.

A strap that is made of leather. Usually composed of two pieces.

A nickname for a watch whose crown is on the left side of the case as opposed to the typical right side. Other nicknames include ‘destro’, ‘southpaw’ and ‘LHD’.

A nickname for the Rolex Oyster Perpetual Cosmograph Daytona reference 116598SACO, a yellow gold Daytona with round cut diamond hour markers, a bezel set with baguette cut cognac-colored sapphires, end links set with round cut diamonds, and a lacquered dial and leather strap with the eponymous leopard pattern.

A style of movement where the seconds subdial is mounted at the opposite end the crown on the same axis with the crown stem. This would put the crown at twelve o’clock and the subseconds at six, or the crown at three and the seconds at nine. Not all of Jean-Antoine Lépine’s personal creations were so-called Lépine movements, but the name caught on. Antonymous with ‘Savonette’. Today with the proliferation of wristwatches, the Lépine movement is somewhat rare - virtually all wristwatches have their crown at three and either a central seconds or subseconds at six. However, this arrangement is still common in chronograph wristwatches where the the running seconds is often at nine.

Not to be confused with ‘Lépine (movement style)’. A movement architecture made of a single plate and bridges instead of the bulkier two plates and pillars, and using a wheel train connected to a toothed mainspring barrel instead of the much bulkier fusée-and-chain. These improvements alone made the movement significantly smaller, freeing up room for the balance which was previously mounted on top of all the clockwork. Lépine’s innovations virtually halved the thickness of portable timepieces and changed watch movement design forever. Some experts classify the Lépine calibers into five generations. See ‘Lépine I’ to ‘Lépine V’ for more information.

A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1800 to 1825. Equipped with a double-geared spring limiter or a Geneva stopwork. Used a cylinder escapement.

A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1825 to 1835. Distinguished by a large yoke-shaped bridge that covers half the mainspring barrel. The center wheel cock and center wheel are above the balance wheel. Mostly cylinder escapements with some lever escapements.

A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1830 to 1840. Distinguished by the introduction of a barrel bridge and separation of cocks (one wheel, one cock). Lépine IIIs have radial cock arrangement with few exceptions. Increasing adoption of the lever escapement while cylinder escapement retains dominance. Over the course of the Lépine III the mainspring ratchet click migrates from the center of the barrel bridge to its side.

A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1835 to 1850. Center wheel is now held by a bridge instead of a cock. The Lépine IVs coincide with the start of mass production and have a great deal of variability in design, finishing, and features.

A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1850 to 1825. Lépine Vs are easy to identify due to their parallel bridge and cock arrangement, doing away with the radial arrangement of previous generations. Full dominance of lever escapement with the exception of low-end movements with cylinder escapement. Very rare examples have detent escapements. Some later versions of the Lépine V caliber are stem-wound (via crown) instead of key-wound.

See ‘open face’. Antonymous with ‘savonnette (watch)’ and ‘hunter watch’.

A style of indices/markers in the form of letters or characters. They may spell out a mantra or the name of the owner. In pocket watch collecting, these markers are more commonly called ‘runic markers’.

An escapement that utilizes a pivoted lever to engage the balance wheel and train. In most designs the lever is a T-shaped pivoted lever which has a claw-like jewel pallet on each end of the horizontal bar and a swallowtail cut at the end of the vertical bar. The pallets lock and release ('draw') the escape wheel while the swallowtail interacts with a protrusion on the balance wheel called the impulse pin. The lever serves as a perfect mediary for the train and balance as its constant collision with the impulse pin provides impulses to keep the balance running, but the speed at which the impulse pin hits the lever is determined by the preset amplitude of the balance. The lever escapement is known for its combination of accuracy, durability, serviceability, and reliability. It is also a self-starting escapement. Also see 'English lever escapement' and 'Swiss lever escapement'.

A pocket watch that has a setting lever which must be first engaged to set the time. When engaged the lever allows the crown to move so that the time may be set. When returned to rest the lever prevents the crown from moving. The lever itself is hidden in a cutout under the dial which requires the bezel to be removed and a fingernail or pin to fish the lever out of its resting position. This arrangement makes setting a deliberate action, and is therefore used in high-grade pocket watches that are so accurate that they do not need to be set often anyway. They are thus common in 19th century railroad pocket watches.

‘Left-hand Drive’. A nickname for a watch whose crown is on the left side of the case as opposed to the typical right side. Other nicknames include ‘destro’, ‘southpaw’ and ‘lefty’.

(German) Lithographie, galvanoformung, abformung. ‘Lithography, electroplating, and molding’. In watchmaking, LIGA refers to a manufacturing process that is used to manufacture small components with high precision through photolithography to make molds, and then electroplating/electroforming the final product in galvanic bath.

A semiconductor device that emits light when an electric current flows through it, or a display that is made up of such devices. In watchmaking, they are most commonly used for displaying the time in electronic digital watches using seven-segment and/or dot matrix. LEDs emit their own light and thus do not need a backlight to be visible in the dark. LED displays are now less common than LCDs.

A type of quartz movement that is able to replenish its power via exposure to light, especially sunlight. This is achieved through photovoltaic cells on the dial which convert light to electricity, which is then used to charge a capacitor or rechargeable battery.

A unit of measurement corresponding to 2.2558mm, or twelfth of a French inch/pouce (27.07mm). Abbreviated with a triple apostrophe ('''). The word is used in its original French form (pronounced [leen]), although 'line' and 'Paris line' are also used. 'Ligne' is still used most commonly to avoid confusion with an English line, which is a twelfth of an English inch and thus slightly shorter than its French cognate. Ligne is an obsolete unit of measurement vestigially used only by the Francophone watchmaking industry.

Military timezone name for UTC-11.

An edition of a watch that is limited to a specific predetermined production number. Compare with 'limited production'.

An edition of a watch that is limited in production but not to a predetermined number of watches. There may be an annual cap on production numbers or a limited period of time the watch may be produced. Compare with 'limited edition'.

The underside of a watch strap. Many straps such as most fabric straps and rubber straps do have a separate lining. Lining is usually done with a softer material as it makes direct contact with the wrist. It may also use a material better for absorbing sweat.

An electronically modulated optical device that uses liquid crystals and polarizers to display information. An electric current alters the form of the liquid crystals, either allowing light to pass through or not. In watchmaking, they are most commonly use for displaying the time in electronic digital watches using seven-segment and/or dot matrix. They are capable of displaying higher resolution images than LED displays, but they are not inherently luminescent unlike LEDs. Therefore, they are illuminated by backlights. LCDs are the most common display used in digital wristwatches.

An escapement which utilizes the constant flow of liquid. Usually they were in the form of a container which performed an action once a sufficient amount of water was poured into it. Liquid escapements were essential in clepsydras which were important timepieces before the introduction of mechanical clocks.

Lunette Noire. Rolex nomenclature for a black bezel.

A nickname for the Omega Speedsonic references 188.0001 and 388.0800. The name comes from the watches’ case and bracelet which resemble a lobster shell.

The time where one is.

A hand style that consists of a thin straight shaft culminating in a circle (usually lumed) and a small tip. Almost exclusively used for seconds hands.

A clock style with a tall box body that accommodates a swinging pendulum.

A watch manufacturer established in Saint-Imier, Switzerland in 1832. Longines is owned by the Swatch Group.

See 'keeper'.

A casting technique where a wax or resin duplicate of the final product is sculpted to make an intricate mold cavity. The wax duplicate is melted away once the mold around it is complete, hence the name ‘lost-wax’. It is the only casting technique that is intricate enough to make components for watches. However, even lost-wax casting is an extremely rare process in watchmaking.

A style of hands distinguished by a complex scroll pattern towards the base. Louis XIV hands are not lumed.

A magnifying device designed to be held or worn close to the eye. While most loupes are simple cylinders with a flared end for the eye, some loupes are designed to be mounted to headgear or glasses. Loupes typically provide 3x to 16x magnification and are used ubiquitously in the horological community by everyone from enthusiasts to watchmakers.

A tool that allows a watchmaker to fasten a loupe to the eye, freeing the hands to work on the watch. Loupe holders are often wires but can come in more sophisticated forms.

A timepiece's ability to withstand sudden pressure differences between the air inside the case and outside of it. This was particularly a concern for aviators who experienced blown-off crystals after a fast climb because the internal pressure of the watch was still at surface pressure, or one standard atmosphere. This is a less common issue today due to better manufacturing techniques. A similar pressure-related problem still exists for dive watches which surface from saturated diving. See 'helium escape valve' for more.

An arm-like appendage of a wristwatch that allows it to be attached to a band. Most wristwatches have four lugs in two pairs at the twelve o'clock and six o'clock positions. Each pair of lugs has a removable metal bar in between that allows a band to be attached. See 'spring bar'. Some wristwatches combine the pair of lugs and the bar in between into a single unbroken piece of metal which makes the construction more solid but the variety of compatible bands limited. See 'fixed lug'. Some watches have no dedicated lugs and instead have an integrated band. See 'integrated band'.

The horizontal distance between a pair of lugs. Lug width is necessary for sizing straps or bracelets. Not to be confused with 'lug-to-lug'.

The vertical distance between the twelve o'clock and six o'clock extremities of the watch head, which would normally be the top and bottom lugs. Lug-to-lug measurement is important for understanding the true size of a watch as the wearing experience also depends on the size and shape of the lugs and case profile and not just the more commonly understood case diameter. Not to be confused with 'lug width'.

A case with no visible lugs. Any lugs on a lugless case are called ‘hidden lugs’. Some lugless cases literally have no lugs, and have a completely unremovable bracelet attached to the case. This is somewhat rare in the modern day as even watches with integrated bracelets have removable bracelets even though their lugs are very unconventional.

Luminous material which allows the clock to be read under low light conditions. Lume can be found on the hands and/or dial.

A patch of lume.

A picture that captures the luminescence of a watch's lume.

Lunette Verte. Rolex nomenclature for a green bezel.

Another name for twisted lugs. It is most often used to describe the twisted lugs of the Omega Speedmaster and similarly-profiled lugs. The name likely comes from how the side profile vaguely resembles a lyre.

A timepiece's ability to maintain an acceptable level of performance after exposure to a magnetic field. Magnetic resistance is measured in the units of magnetism such as gauss (G), ampere per meter (A/m), and tesla (T). Magnetic resistance is usually achieved with special nonmagnetic components or a magnetically conductive shield for the movement.

An inset magnifying lens on the crystal which increases the legibility of whatever is under it. Magnifiers are usually attached over the date window.

See ‘German silver’.

A large plate which serves as the structural foundation of a movement. Virtually all movement components are anchored to the main plate, either directly or via bridges.

A large spiral torsion spring which stores and releases energy in a mechanical movement, serving as its power source. The mainspring is fixed to an arbor (axle) on one end and the inner wall of the barrel on the other. The natural tendency of the spring to uncoil after being coiled through winding moves the teethed barrel in which it is housed, which in turn moves the gear train. Not to be confused with 'balance spring' or 'hairspring'.

A gemstone of the copper carbonate hydroxide variety, sporting a deep and opaque blue-green to green hue with wavy and swirly banding. In watchmaking, malachite is typically used to make rare stone dials.

See ‘Geneva drive’ and ‘Geneva stopwork’. An alternate name for the Geneva drive and stopwork due to the driven wheel’s resemblance to a Maltese cross. The four-armed version almost completely resembles a Maltese cross, but this variant is used more commonly in non-horological clockwork like old cameras and projectors where the rotational energy of a crank must be translated to intermittent motion. In watchmaking the mechanism is mostly used as a stopwork, which means that the driven wheel cannot have even arms - one must always be big enough to set a limit to the number of rotations that a barrel performs. In this instance the even arms still resemble those of a Maltese cross thanks to their V-shaped profiles.

A clock style designed to be placed on a mantel.

A movement which must be wound manually. Synonymous with 'hand-wound' and 'manual wind'. For the vast majority of cases, refers to a type of mechanical movement although there are some exceptions like manually-wound hybrid movements. Also called simply a 'mechanical movement' by some although this term can be technically erroneous and potentially confusing.

(French) Manufacture d'horlogerie. In watchmaking, a 'manufacture' is a watch manufacturer that develops, designs, makes the parts of, assembles, and tests its own watches as opposed to having a significant portion of the aforementioned process done by other companies. Today a similar term 'in-house' has gained more currency, but manufacture refers to the company itself whereas in-house refers to a certain product.

(French) A factory which makes its own components. See ‘manufacture’.

The Marina Militare is the Italian Navy. Several watches associated with or issued by the Italian Navy are dubbed the ‘Marina Militare’, including various Panerai wristwatches over the years and the Citizen Promaster NY0040.

A nickname for the Citizen Promaster NY0040 dive watch that is commonly associated with the Italian Navy. It is believed that a special 500m-rated variant was created for or ordered by the Italian Navy’s special operations units. Documented evidence regarding this order is lacking.

An extremely accurate timepiece - usually a clock but sometimes a watch - meant to be used onboard watercraft for navigation, timekeeping, and communication, or a wristwatch that is inspired by the aesthetics of the former. The latter is also commonly referred to as a 'marine watch'. Marine chronometers were kept on a gimbal system mounted inside a protective box in order to keep it level against the rocking motion of a surface vessel. They typically had simple, legible white dials and a power reserve indicator so that the crew could prevent the chronometer from running out of power.

A category of wristwatch based on the marine chronometer. Sometimes 'marine chronometer' and 'marine watch' mean the same thing. Marine watches supplemented the larger and more accurate marine chronometers that were kept in gimbaled cases. With the advancement of wristwatch accuracy they were impressive timekeepers of their own right. A typical marine watch has big, bold Arabic or Roman numerals in black against a white dial, and sometimes a power reserve indicator reminiscent of those found on marine chronometers.

A wristwatch made of components from different watches, especially one that combines the movement of an older watch and a newly-made case. Marriage watches are a popular way of using fine pocket watch movements that would otherwise no longer be used. There is some overlap with the term 'frankenwatch', which carries a highly negative connotation. Generally 'frankenwatch' is used to describe a watch that tries to pass off as genuine and combines anachronistic parts. Even some honest marriage watches which mimic the signature of the movement manufacturer on the dial are seen to border on frankenwatch territory. However, the practice of recasing old movements itself is an old and time-honored tradition.

A style of indices/markers in the form of Masonic symbols, commonly including the All-seeing Eye, trowel, Sun, Moon, compass, square, gavel, beehive, and skull. These are used in Masonic watches.

A watch that incorporates design elements of Freemasonry, sometimes designed for Freemasons but also commonly offered as quirky dial options. Most designs feature various Masonic symbols as indices while some feature triangular cases.

(French) See 'inertia block'.

A clock that serves as a time standard and controls other devices dependent on a time signal. The term generally refers to now-antiquated master clocks of the 19th and 20th centuries and not our modern day atomic clocks which send time signals to electronic devices. However, any clock that serves as the supreme timekeeping device of a clock network is technically a master clock. The archetypal master clocks of old were connected via electrical wires to various devices including time card punches, school bells, sirens, and slave clocks in individual classrooms or clock towers. They were often long case pendulum clocks.

A watch manufacturer established in Zürich, Switzerland in 1975. Maurice Lacroix is privately owned.

A dial with enlarged markers, text, or other features. Typically used in Rolex nomenclature for Submariner references 5513, 5512, 5517, and 1680 as well as GMT-Master II references 1675 and 16750. These watches were produced in the 1970s. However, the Maxi configuration is standard for all Rolex watches today that have diver markers.

A watch manufacturer established in Geneva, Switzerland in 2005. MB&F is privately owned.

An escapement which only utilizes purely mechanical components instead of fluid or electricity.

One of the three major types of movement. A movement that uses purely mechanical clockwork, i.e. a mechanism of springs, levers, gears, pulleys, and/or weights to measure and display the time. A mechanical movement has no components that generate or use electricity or magnetism. Additionally, a mechanical movement may refer to a 'hand-wound mechanical movement' or 'manually-wound mechanical movement' which is a mechanical movement whose mainspring must be manually wound as opposed to an 'automatic mechanical movement' which does not require the wearer's intervention to be wound. This usage, while common, is at times technically erroneous and potentially confusing.

A meeting of watch collectors of a certain community, society, club, or for a certain event. Meet-ups are opportunities for enthusiasts to connect with other enthusiasts and try on different watches. Also known as a 'get-together' or 'gtg'.

A type of LCD technology that utilizes a built-in memory for every pixel in the form of static RAM (SRAM). MIP displays are power efficient because the built-in memory in the pixel obviates the need for the processor to constantly refresh the on-screen image - a pixel will remember to stay as is if change is not necessary even without input from the processor. MIP displays also boast superior readability and clarity of image as they place the reflector layer in the middle while conventional displays place it at the bottom. This eliminates the shadow typically seen in most other displays and allows for a flat image that is much clearer and crisper in sunlight.

Microelectromechanical systems. A technology in which both electronic and mechanical components make up a microscopic machine. This term is used most in the context of semiconductor production. In watchmaking, MEMS refers to the application of the MEMS fabrication technology of photolithography to the manufacture of watch components. Photolithography utilizes light to lay down a thin protective layer over a substrate so that the uncovered areas can be etched away. This method is ideal for making intricate microscopic components and produces far more precise and smaller products than those made with traditional metalworking techniques such as cutting, milling, stamping, or casting. Thus it can be used to create the smallest and most important components of wristwatches. The technology is most associated with Japanese watchmaker Seiko.

A watch designed with a male wearer in mind. Modern men's watches typically range from 36mm to 45mm in case diameter.

A style of hour hand that is distinguished by a disc towards the tip with veins in the shape of a three-pointed star that resembles the emblem of Mercedes-Benz. The Mercedes hand can be considered a variation of the cathedral hand. They are always lumed.

A bracelet with small chain-like links that mesh together like mail. Also called 'Milanese mesh' or 'shark mesh'. The name 'Milanese' comes from the weaving pattern's purported origins in Milan, Italy. 'Shark' mesh likely comes from an Omega advertisement which dubbed the bracelet 'sharkproof'.

Federal Institute of Metrology. The Swiss national institute for metrology. In watchmaking, METAS most commonly refers to the METAS Master Chronometer certification which certifies the accuracy and precision of timepieces under various conditions.

A nickname for the Heuer Carrera reference 1153N chronograph. The name comes from British singer and songwriter Sir Mick Jagger, who famously wore the watch.

A feature of certain clasps that allow the wearer to adjust the anchor point of the strap to the clasp. Clasps with microadjustment will usually have six or more microadjustment holes with 2mm or 3mm spacing. Microadjustment makes up for the lack of adjustability in clasps compared to buckles. Also see 'quick adjustment'.

See 'integrated circuit'.

A unit of length that is one millionth of a meter. More commonly called ‘micron’. In watchmaking, micrometers are most commonly used to measure the thickness of gold plating.

The non-SI but more popular term for the micrometer. See ‘micrometer’.

A type of oscillating mass in an automatic mechanical movement that is completely horizontally integrated into the movement rather than placed on top of it. The microrotor allows an automatic movement to be significantly thinner due to the elimination of the concentric rotor-weight while providing a better view of the other components of the movement that would otherwise be covered by a large concentric rotor.

Military timezone name for UTC-12.

Military specification. Also spelled ‘MIL-SPEC’ and ‘milspec’. In watch collecting, mil-spec refers to watches and watch accessories manufactured to, or modified to conform with specification requirements set by a military organization. Watches that were adopted by military units without modification from their commercially available form are not typically called mil-spec.

(French) Short for 'maille milanaise' Milanese mesh.

A style of mesh bracelet with a weave pattern believed to originate in Milan. Known as 'maille milanaise' in French. Milanese meshes tend to have the visible part of the link run parallel with the strap or very slightly diagonal. Also see 'Polish mesh'.

A dial made for or by a military, or one inspired by such dials. Like the term ‘military watch’, the word is loose and does not hold much meaning as is without further elaboration. In the most common sense, the most widely recognized military dials originate from designs finalized during the Vietnam War, where a combination of lumed geometric markers, 12-hour and 24-hour notations, and high-contrast, simple color schemes were set as a uniform standard for watches issued to American troops. Watches with both 12-hour and 24-hour notations are colloquially referred to as military dials.

A convention of timekeeping used by the military. While not all militaries use the same convention, timekeeping is somewhat uniform around the world. Military time uses the 24-hour notation to avoid ambiguity, typically with no colon (:) in the middle to separate the hours and minutes, and may be accompanied with an alphabetical designation to denote the time zone.

A catch-all term for all watches associated with the armed forces, paramilitaries, and private military organizations. In the narrowest sense it refers to 'issued watches' - watches issued by the military itself - and watches designed for use by military personnel. In a broader sense it may refer to any watch used extensively by military personnel regardless of original intent. Naturally military watches may refer to field watches, dive watches, pilot's watches, and any other category of watches that various types of soldiers may find useful.

(Italian) ‘Thousand lines’. A nickname for the first style of screw-down pushers used in Rolex Daytonas, namely on reference 6240.

A metalworking technique that involves the machine-cutting of a metal workpiece with a milling cutter into a desired shape. Milling is a complex and precise technique that works with a solid metal workpiece. Hence, it is the most expensive but creates the heaviest, most durable, and most intricate product. Milling is appropriate for machining complex components such as cases or solid components such as crowns. On more costly timepieces, every metal component including the bracelet links and clasp are milled.

A nickname for the Rolex Oyster Perpetual Submariner references A/6538, 5513, 5517, and 5513/5517 that were modified for and issued by the Ministry of Defense of the United Kingdom. The name is a portmanteau of 'military' and 'Submariner'. Of these, the A/6538 is sometimes separated from the latter three as it was a low-production prototype that many do not regard as a full-fledged Milsub. The latter three Milsubs share certain modifications such as a larger and grippier fully-graduated bezel, tritium lume, fixed lugs, sword hands, and military markings on the caseback.

A silicate glass that is heat and chemical treated for increased hardness. Untreated mineral glass rates around 5 on the Mohs hardness scale while treated glass rates up to 7. Mineral glass stands in the middle of the road in the watch crystal spectrum. It is softer than sapphire and harder than acrylic, heavier than acrylic but lighter than sapphire, and more expensive than acrylic but cheaper than sapphire. Unlike acrylic, mineral glass shatters on strong impact much like sapphire and cannot be polished.

See ‘radial dial (Rolex)’.

A condition level that indicates that the timepiece is the exact condition it left the factory. It may have been taken out of its packaging and even worn a couple of times, but there must be no change in condition from its original condition. A common but erroneous understanding prevalent in the watch collecting community is that 'mint' means 'very good condition'. Mint watches must be flawless regardless of circumstance where as any other condition level may factor in the age of the watch.

The hand that points to the minute. Makes a full rotation every hour.

A rack which interacts with the minute snail and the hammer trip of the treble hammer. It is lined with fourteen teeth, one for each minute between full quarters.

A component of a chronograph mechanism that applies constant pressure to the minute recording wheel so that the chronograph minute hand advances in the desired manner and so that bumps and knocks do not throw off the position of the chronograph minute hand.

A component of a chronograph which moves the chronograph minute hand.

A striking complication that repeats the hours, quarters, and minutes since every quarter on demand. Typically the hours are sounded with a bass note, the minutes with a treble note, and the quarter with one bass and one treble. For example, 02:47 would be "dong, dong, ding-dong, ding-dong, ding-dong, ding, ding".

A snail cam which transmits information on the current minutes to the minute feeler so that a repeater can announce the current minute. The minute snail is in the shape of a four-pronged pinwheel/curved swastika, each arm (representing a quarter) with fourteen levels cut out like a sawtooth.

A component of the motion work that serves as the reduction gear for the hour hand. It meshes with the cannon pinion and is designed to rotate once every twelve hours, which is usually achieved by having a much larger circumference. The minute wheel’s coaxial pinion meshes with the hour wheel. Unlike what may be inferred from the name, the minute wheel does not control the minute hand. Therefore it should not be confused with the second wheel, which is sometimes called the ‘minute’ or ‘minutes’ wheel because it is responsible for turning the minute hand.

See 'mirror polish'.

See 'black polish'. Generally mirror polish is also seen as a somewhat less fine level of finishing than black polish, although the definitions are not clear. In many cases they are used interchangeably.

A track or chapter ring that has a shiny, mirror-like finish when the rest of the dial is a different texture.

A designation for a timepiece with Swiss origins but no other information regarding the manufacturer or brand.

A nickname for the Omega Speedmaster Professional reference 3570.31.00 limited edition specially made for the Mitsukoshi department store in Japan.

A style of indices/markers that draw from two or more styles of markers for aesthetics or legibility. A very common style is the mix of Arabic numerals and batons. A famous style of mixed markers is the so-called ‘California’ markers, which uses Arabic and Roman numerals.

An aftermarket modification of a watch. The term typically refers to modifications done by switching certain OEM parts for third-party ones instead of more laborious and technical customization jobs done by personalization/customization specialists. However, any modification can technically be considered a mod. In most cases including the most expensive mods, the movement is left untouched. Some modders do tweak the movement, usually by skeletonizing the plates and bridges for visual effect.

A nickname for Omega Seamaster 300 dive watches ordered by the British Ministry of Defense in the 1960s and 70s. These are mil-spec variants of the reference 165.024, ordered between 1967 and 1971.

A chronograph mechanism that is designed as a separate mechanism that can be attached to a movement as opposed to one that is a native part of it. Antonymous with ‘integrated chronograph’. Modular chronographs are popular options for companies that do not wish to invest resources on developing an integrated mechanism. As an integrated chronograph is sold as a module, the mechanism is usually bunched up under a single plate or bridge and has its own mainplate. This may sometimes prove trickier or easier for servicing depending on the issue. The chrono hands on modular chronographs also typically tend to jump as if startled on operation. Nonetheless, modular chronographs vary greatly in quality and some boast excellent features.

An independent assembly of components meant to perform a specific function, especially as an add-on to a preexisting movement. Modules are typically designed by specialty manufacturers for complicated mechanisms such as chronographs that are difficult and costly to develop in-house. A complication or movement can be described as 'modular' if it utilizes a module. Not to be confused with 'module (quartz)'.

A quartz movement. Not to be confused with 'module (mechanical)'.

A nickname for the Seiko SRP585, SRP587, SRP589 and other similar divers with a raised twenty-minute section on the rotating bezel that resembles a mohawk.

(Japanese) A nickname for the Grand Seiko reference SBGH269 which has a red dial reminiscent of autumn leaves. 'Momiji' is Japanese for 'red leaves', 'autumn colors', or the Japanese maple.

A nickname for the Seiko 7016 and 7018 series automatic flyback chronographs with a rectangular case reminiscent of the iconic Heuer Monaco.

A chronograph that has a chronograph seconds hand that can be stopped while the chronograph is running and then released to catch up to the position corresponding to the current elapsed time. For example, if the chronograph was stopped at 15 seconds and held for thirty seconds, releasing the pusher would launch the chronograph seconds hand to the 45-second position to resume timing. It is essentially a simpler version of the split-seconds chronograph/rattrapante with the same ‘catch-up’ function but with only one chronograph seconds hand and no dedicated split pusher. The mono-rattrapante is an extremely rare complication.

A case that is fashioned out of a single solid block of metal instead of assembled from parts. A monobloc case lacks a separate caseback. This means that movement maintenance can only be performed by completely removing the movement through the front opening. However, monobloc cases offer better protection against water and dust in theory as they eliminate a potential weakness of the case. Some monobloc cases are engineered to keep out even helium atoms, thus eliminating the need for helium escape valves. With modern technology monobloc cases are practically a stylistic choice as threaded casebacks are more than sufficient.

(Italian) Monobloc. A nickname for the Rolex references 3525 and 4500. The name refers to the fact that the bezel, lugs, and case are all milled out of a single block of metal, as opposed to many other watches where the lugs are attached later and the bezel is removable.

A chronograph with only one pusher for start/stop and reset as opposed to the now-conventional assortment with two pushers. As there is only one pusher, a monopusher chronograph can only operate linearly - the order of operation will always be start, stop, and reset, with no possibility of resuming timing after the chronograph is stopped unlike in a two-pusher chronograph which can be stopped and resumed an unlimited number of times. Monopushers were the standard until the introduction of the two-pusher chronograph which is superior in usability and practicality. However, monopushers are still quite common today as they offer a simpler look and can be integrated into the crown. They also have the advantage of being impossible to fumble because one cannot press the pushers in a wrong order.

A nickname for the Seiko SKX779 diver and the various divers that take after it. The name comes from the aggressive bezel, bold and teeth-like indices, and large hands.

A nickname for the Tudor Oysterdate references 7149/0, 7159/0, and 7169/0. The name is a reference to the historic Monte Carlo casino, as the unique design of the watch is reminiscent of a roulette wheel.

A style of dial in railroad pocket watches that generally features the following: an indication of the hours from 1 to 12 in large bold Arabic numerals, a seconds sub-dial at 6 o’clock, and 60 Arabic numeral minute markers in an upright position called a ‘marginal minute track’, with every five-minute marker in red. Many but not all Montgomery dials featured an additional ring of hour markers in a smaller font. Some but not all also featured a 6 o’clock hour marker inside the seconds sub-dial instead of leaving it blank like most watches. Designed by Henry S. Montgomery in 1899, the name has been applied to a broad range of similar dials. Also called the ‘Safety dial’.

A style of dial in railroad pocket watches that features the following: an indication of the hours from 1 to 12 in medium-sized bold Arabic numerals towards the center of the dial, a seconds sub-dial at 6 o’clock, very long minute hashes, and 60 Arabic numeral minute markers in an upright position called a ‘marginal minute track’, with every five-minute marker in red. Designed by Henry S. Montgomery in 1918 as an improved design to his original dial, the Type II dial was created with the belief that fewer mistakes are made when reading the hours than the minutes.

(French) A watch or clock.

(French) School watch.

A nickname for the Omega Seamaster Chrono-Quartz reference ST396.0839. The name comes from the both the circumstances of its release and composition of the display. The watch was created for the 1976 Montreal Olympics and resembles the event’s main analog-digital scoreboard. The same watch is also called the ‘Olympic’ and the ‘Albatross’.

A style of hands distinguished by a ring towards the tip. The more popular ‘Breguet hands’ are considered a style of moon hands, but moon hands typically have an untapered, straight body and usually have long pointer tips as apposed to the triangular tips on Breguet hands. The two terms can be used interchangeably. Moon hands are not lumed.

A calendar complication that displays the shape of the moon for a given night. It looks similar to, but should not be confused with, the day-night complication.

A nickname for the Omega Speedmaster Professional reference 105.012 and all Speedmaster Professional chronographs that follow in its pattern. The ref.105.012 was issued to the astronauts of Apollo XI and in 1969 was the first timepiece worn on the lunar surface. Since the success of the lunar mission, Omega has always kept a Speedmaster Professional in their product lineup that preserves the old-school formula of the Speedmasters of the time: a manually-wound, triple-register, 12-hour, no-date, stainless steel chronograph with an option for a solid caseback and hesalite crystal. These subsequent generations of the Speedmaster Professional are all called Moonwatches and contrast with other Speedmasters that incorporate the newer designs, materials, and complications of their time.

A nickname for the Seiko Superior 3883-7000 which has an textured and mottled iridescent blue dial. The nickname is likely a reference to a genus of butterflies which is known for having many species with metallic blue or green wings. The watch is also called ‘Butterfly’ and ‘Peacock’.

An iridescent material that forms the inner shell layer of certain mollusks such as abalones, pearl oysters, and some mussels. While the material is more formally known as ‘nacre’, ‘mother of pearl’ is the far more dominant name in watchmaking. In watchmaking, mother of pearl is most commonly used to make exotic watch dials.

A mechanism that turns the hour hand with the minute hand via a reduction drive. As the hour hand needs to turn twelve times slower than the minute hand, a 12:1 gear reduction is necessary. The motion work consists of the cannon pinion, minute wheel, and hour wheel.

A machine that converts electrical energy to mechanical energy. In watchmaking, motors usually refer to the motors in analog electronic watches which move the hands and other mobile components of the watch. There are largely two types of motors: the step motor and non-step motor.

A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1881 and now headquartered in Paramus, USA. Movado is owned by the Movado Group.

The mechanism of a timepiece which measures and displays the time. Also called a 'caliber' especially when referring to a specific movement. In electronic watches the movement is sometimes called the 'module'.

A tool that holds a movement that is removed from its case. Movement holders can look like adjustable vices or come in dimensions dedicated to a specific movement.

A nickname for the Grand Seiko reference SBGJ001/021 GMT and all other watches with the same 'Mt. Iwate' dial texture. The dial texture was inspired by and gets its name from the ridges of Mt. Iwate, a snow-capped stratovolcano located near Grand Seiko's Shizukuishi Watch Studio in Iwate Prefecture, Japan.

A watch manufacturer established in Glashütte, Germany in 1869. Mühle-Glashütte is privately owned.

A derisive name for fake watches assembled in India, especially Seiko 5s.

A switch, button, or slide which disarms the striking complication, preventing it from making any sounds. It may also be used to silence an ongoing chime.

A nickname for Rolex dials with a gem-set hour marker ring. Blue dial variations are specifically called ‘blue myriad’ dials.

A general nickname given to certain analog dials with unconventional ways of displaying the time, typically employing discs instead of hands as indicators. This can refer to hands mounted on sapphire discs to give the appearance of floating, or rotating discs with an arrow instead of a hand to indicate the time.

See ‘mother of pearl (MOP)’.

A style of one-piece strap that is constructed using two connected pieces. Also called a NATO strap, it is usually made of a fabric like nylon. The long piece, which is sewn and glued to the top of the short piece, is pulled through the watch's lugs and then through a metal keeper fixed at the end of the short piece. The remaining strap length is tucked and organized with two fixed keepers. This effectively fastens the watch not to the wrist but to the strap itself. If a spring bar fails due to high impact or abrasion, the watch head will dangle from the strap instead of coming off the wrist like it would with a two-piece strap. Nato straps were first developed for the military but are now adored by others who would need a cheap and failsafe strap like surfers, divers, outdoorsmen, and anyone who appreciates the aesthetic. Also see 'zulu strap', 'nato zulu strap', and 'RAF strap'.

A style of one-piece strap that is constructed using two connected pieces. It is usually made of a fabric like nylon. Like the name implies, the nato zulu strap is a hybrid of the nato and zulu straps. It uses the two-piece construction of the nato strap while using zulu-style hardware. Unlike a zulu strap which has three hoops/rings to organize the unused length of the strap, a nato zulu has two additional rings in lieu of the nato's fixed keeper at the end of the short piece. This is why it is also called the five ring zulu. The advantages of the nato zulu strap are primarily reduced pressure on the strip bars and its variable strap length. The long piece can be pulled through the two extra hoops twice to shorten the strap, and just once to reveal its full length. This is useful when wearing the watch over the cuff. Also see 'nato strap' and 'zulu strap'.

An electronic digital display (LCD or MIP) where the assets are presented in a lighter color than the background.

In watchmaking, 'neo-vintage' refers to an object that is approaching vintage status. As of the 2020s, neo-vintage refers to watches produced in the 1990s and 2000s.

A timepiece is considered new old stock when it is both (i) a reference that is no longer in production (old stock), and (ii) in mint condition (new). The term is used mostly for vintage timepieces but any timepiece regardless of production year can be new old stock as long as it is no longer in production.

‘Not For Sale’. Watch collecting social media abbreviation to indicate that a watch is not available for purchase. Also see ‘FS’.

In watchmaking, a nickname is a colloquial, usually-unofficial monicker given to a watch that captures a distinct quality. It is different but sometimes related to the official name of a watch. Watch manufacturers and certain movements may also have nicknames.

A nickname for Universal Genève Compax reference 885103 chronograph, and sometimes the similar ref.885105, ref. 885107, and ref.885108. The more famous panda dial ref.885103/1 is known as the Nina Rindt as it was worn prominently by fashion icon and model Nina Rindt to her husband Jochen Rindt’s races. (Her husband wore a Heuer Autavia, see ‘Jochen Rindt’) She wore the watch on a leather cuff. The reverse panda ref.885103/2 is called the ‘Evil Nina’. References 885107 and 885108 are called ‘Exotic Nina’ due to their exotic dials.

A style of indices/markers in the form of a raised circular metal base with a spot of lume at the top, observed by some to be reminiscent of a nipple. The name is most associated with Rolex watches, namely certain GMT-Masters and Submariners produced from the 1950s to the 70s.

A watch manufacturer established in Grenchen, Switzerland in 1926 and revived in 2018. Nivada Grenchen is privately owned.

A nickel iron alloy commonly used for hairsprings, produced by a company of the same name. The name stands for 'nicht variabel oxydfest', German for 'non-variable, non-oxidizing'.

A company that produces watch components, especially components made of its proprietary alloy. The name stands for 'nicht variabel oxydfest', German for 'non-variable, non-oxidizing'. Nivarox is owned by the Swatch Group.

A watch manufacturer established in Glashütte, Germany in 1990. Nomos is privately owned.

In Rolex collecting nomenclature, a ‘non-step dial’ specifically refers to the flat, un-stepped dial fitted to certain Rolex ‘Paul Newman’ Daytona chronographs. This is in contrast to the ‘step dial’ which has a noticeable step, or height difference, from the border of the dial with the minute and hour markers and the main dial. Non-step dials are considered inauthentic, and derisively called ‘Texas dials’ due to an alleged association with Texan counterfeiters. A non-step dial may have been manufactured by the correct dial supplier - Singer - but nonetheless were not fitted to original Rolex ‘Paul Newman’ Daytonas.

A motor that does not step bur rather moves in a continuous motion. One of the two types of motor. Sweep motors are less common in quartz watches because of their large energy consumption compared to step motors. Timepieces with sweep motors can be identified with unbroken movement of the seconds hand.

A signal gun which fires at noon.

Military timezone name for UTC+1 or UTC-13.

A type of leather. Nubuck is a top-grain leather that is buffed to a smooth, velvety finish much like suede/split grain leather. As it is a top-grain leather, nubuck is far more durable and water resistant than suede. However it is also more expensive.

A numerical marking on a dial which indicates the hours. A type of index, although an index usually refers to a non-numerical hour marker.

Watch collecting social media lingo meaning 'New Watch Alert'. Accompanied by a photo of a newly acquired watch.

See 'gasket'.

A style of hands distinguished by a broad base tapering gently to a thin neck with a triangular tip. The obelisk hand resembles the namesake obelisk in architecture. It is sometimes alternatively spelled ‘obélisque’ from French.

An installation and facility built for the observation of various events. In the watch world, the term refers to an astronomical observatory which surveys and studies the movement of celestial objects. These observatories were also involved in timekeeping as human time relies on the movements of the Earth, Sun, Moon, and sometimes stars. These observatories often held accuracy competitions which many watch manufacturers used to test the accuracy of their movements. Also see ‘observatory chronometer’.