Watch glossary

ACRYLIC CRYSTAL

Acrylic crystal, also known as plexiglas or plastic crystal, was initially introduced in the 1920s. Unlike sapphire glass, it can be polished, but its main disadvantage is the fact that it scratches easily.

ALARM

Alarm is a function on a wrist watch that makes a sound or a vibration at a preset time.

ANNUAL CALENDAR

An annual calendar is a complication (a term used to refer to an additional function on a watch) showcasing at least the date, day and month. Many will also display the moonphase. A watch with an annual calendar correctly adjusts itself to display the number of days in a month and requires only a single manual correction per year (performed somewhere from the end of February to the 1st of March).

ANTI-MAGNETIC

The movement of a mechanical watch can be thrown off balance if it comes in contact with a strong magnetic field. Magnetism is common in loudspeakers, TV sets, kitchen appliances, cars, etc. and nowadays most watch manufacturers claim their watches to be anti-magnetic. This is achieved by using alloys for certain parts, and among them the balance and the escape wheels. Electronic watches are not susceptible to magnetism.

APERTURE

Some watches feature a small opening on its dial, called aperture, that shows indications such as date, hour or day of the week.

ARABIC NUMERALS

The digitas on the dial representing the hours in the Arabic format (such as 1,2,3,4), as opposed to Roman Numerals (i.e. I, II, III, IV).

ARGENTÉ DIAL

“Argenté” is French for “silver”, so an argenté dial is essentially a silver dial.

AUTO ROTOR

Auto Rotor is a perpetual movement invented by Emil Borer in 1931 and patented by Rolex.

AUTOMATIC WINDING

An automatic watch is wound by the movement of a wearer’s wrist. Such movement causes a rotor or a balance weight inside the watch to rotate back and forth. The weight is connected to the barrel arbor (which is hooked to the mainspring) by a gear train, thus winding it and keeping it in constant tension.

BAGUETTE WATCH

The term “baguette” is used to describe an elongated rectangular or an oval shape movement of a ladies’ style watch.

BAKELITE

The transparent acrylic material used on the bezel insert of early Rolex GMT Masters in 1954.

BALANCE

The balance is part of the escapement and regulates the watch. It consists of a metal wheel, now commonly made of Invar (a special steel resistant to changes in dimension due to fluctuations of heat or humidity), and is usually mounted with a hairspring of, also, Invar or a similar alloy.

BALANCE SPRING

Also referred to as the “hair spring”, balance spring controls the swing of the balance.

BALANCE WHEEL

A balance wheel, also referred to as simply the “balance”, is a device that keeps the time between each ‘tick’ constant.

BARK FINISH

Bark finish is the type of finish on bracelet links and/or bezel that rezembles the bark of a tree.

BARREL

Often called the “mainspring barrel”, a barrel is a circular box, often connected to a gear, that holds the mainspring which drives the watch.

BEAT

A beat is a swing of the balance wheel that allows the gear train to advance a set amount, moving the hands forward.A balance’s vibration rate is measured inMeasured in either Beats Per Hour (BPH) or Beats Per Second (BPS). This is the number of times per hour or second that the balance wheel goes through a full arc of motion in either direction. The usual number of Beats Per Hour is 18,000. However, current Rolex watches are 28,800 BPH.

BEZEL

A bezel is a ring around the crystal on the top part of a watch that holds the glass case in place. Can be made from varying materials (i.e. stainless steel or gold) within a watch line.

BICCHIERINI

Bicchierini is what luminous hour markers circled by a ring made of white gold are called. Introduced by Rolex in the mid 80’s.

BI-DIRECTIONAL ROTATING BEZEL

A bi-directional rotating bezel is one that can be rotated either clockwise or counterclockwise and is used for making calculations.

BIG CROWN

The nickname “Big Crown” was given to Rolex Submariner models with 8 mm Brevet winding crown (ref. 6200, 6538, 6540, 5510) by Rolex collectors.

BOMBÉ

The term “bombé” gives origin to the nickname of the Rolex Bombay watch produced in the 50’s and indicates a particular form of the lugs, with a convex profile and helix lines.

BOX & PAPERS

The expression “box and papers” is used to say that a watch comes with its original box, guarantee and accessories, if applicable.

BOY’S SIZE WATCH

A “boy’s size watch” has a smaller diameter than a standard men’s size watch (usually 2 mm smaller).

BRACELET

A watch bracelet is a metal strap that goes around a wearer’s wrist. It is typically made of separate links that can be removed to adjust the bracelet’s length.

BREGUET NUMERALS

Breguet numerals is the Arabic numerals font designed by Abraham-Louis Breguet. 

BREGUET SPRING

The Breguet balance spring was invented by Abraham-Louis Breguet in 1795 and solved the problem of the disturbed rate of balance in flat balance spring by upraising the last coil of the spring and giving it a smaller curve. This Breguet overcoil encouraged the spring to develop concentrically, improving the rate of the watch and reducing the wear on the balance pivots. Currently, most watches feature the Breguet spring as it guarantees a better accuracy of the watch, as well as making it easier to adjust the watch.

BREVET

“Brevet” is derived from the French word “brevette”, meaning “patented”.

BRIDGE

A bridge is any movement plate secured by a minimum of two screws.

BRUSHED

Brushed stainless steel is stainless steel with a matte/satin finish produced by polishing and then softening the metal.

BROAD ARROW

Broad Arrow is the hour hand of Omega’s vintage sports models (i.e. Speedmaster, Railmaster etc.)

BUBBLEBACK

“Bubbleback” is used to describe the early Rolex perpetual models with a thick case that used to house the oversized auto-rotor movement.

BUCKLEY DIAL

A buckley dial is a Rolex dial with big painted Roman markers. These type of dials were the first “exotic” Datejust and Day-date dials and laid the groundwork for the later applied Roman markers.

BUTTERFLY ROTOR

A Butterfly rotor is an oscillating mass with the characteristic “butterfly” shape used on the Rolex 1030 and 1530 calibres and derivatives until around 1963.

CALENDAR WATCH

A calendar watch features a complication (a term used to refer to an additional function on a watch) showcasing the date or the month, day, moonphase and year in the more complex watches. Most calendar watches have to be adjusted manually at the end of the month, but the mechanism of a perpetual calendar watch adjusts itself automatically.

CALIBER OR CALIBRE

Caliber refers to the size, style, or shape of a watch movement.

CALIFORNIA DIAL

A California dial is a dial featuring a combination of both Roman (10 o’clock to 2 o’clock) and Arabic numerals (4 o’clock to 8 o’clock) with 3, 6, and 9 sometimes being replaced with a dash instead of a numeral and 12 featuring an inverted triangle in its place.

CARAT

Carat is weight unit for gems. One carat equals to 0.2 grams.

CARRURE

Carrure is the middle section of a watch case without the bezel and back. 

CARTIER TANK

The Cartier Tank, or simple the Tank, is a line of rectangular watches designed and made by Cartier. The design was inspired by the lines and proportions of the tanks used during the World War I, hence the name.

CASE

A case is the metal housing that contains a watch’s parts.

CASEBACK

A caseback is the bottom of a watch case that can be opened to access the watch’s movement.

CENTER SECONDS

Senter seconds, also called “sweep seconds”, are mounted on the center post of the watch for greater visibility and ease in reading.

CHAPTER RING

The chapter ring is a ring on the watch dial bearing figures and minute marks. The hour figures are sometimes referred to as chapters.

CHRONOGRAPH

A chronograph is a timepiece that also functions as a stop watch and has a separate seconds hand that can be started, stopped and reset to zero with the push-buttons on the side of the watch case.

CHRONOMETER

A chronometer is a highly-precise timepiece tested and certified to meet certain precision standardsby the official Swiss timing bureau Controle Officiel Suisse des Chronometres (COSC).

CLASP

A clasp connects two ends of a watch strap or bracelet and secures it on the wrist.

CLOSED MINUTE DIAL

A closed minute dial features connected minute graduations forming a ring (also known as a continuous minute ring).

CO-AXIAL ESCAPEMENT

In the case of a co-axial escapement, for which Omega holds the patent, the anchor has not two but three anchor forks. The contact between the anchor and the anchor wheel is very brief and punctual. This process creates less friction and the intervals of the oscillator are significantly longer.

COKE BEZEL

A “Coke bezel” refers to Rolex GMT Master’s red and black bezel insert. The name is used to differentiate it from the Pepsi bezel, the name inspired by the soft drink producer’s brand color theme.

COMEX

Comex is short for Compagnie Maritime d’Expertise, a French commercial diving company. Rolex partnered with Comex and it aided in the development of the one-way gas escape valve in the Rolex Sea-Dweller in the 60’s. The Comes Rolex were only distributed within the company, thus making them a prized possession among the collectors nowadays.

COMPLICATION

A complication is a term used to refer to any additional function a wristwatch performs (beyond the basic time telling), such as date, day of the week, moonphase, perpetual calendars or stop/start chronograph functions.

CONCEALED CLASP

A clasp where the buckle is concealed under the bracelet’s links, giving an appearance of a continuous flowing bracelet, is called a concealed clasp. Found on modern Rolex President models.

COSC (CONTROLE OFFICIEL SUISSE DES CHRONOMETRES)

Controle Officiel Suisse des Chronometres (COSC) is the official Swiss timing bureau, where watches are tested for the chronometer rating.

COSMOGRAPH

Cosmograph is a Rolex chronograph with the tachymeter scale printed or engraved on the bezel rather than on the outer rim of the dial. It is a Rolex trademarked term.

CÔTES DE GÈNEVE

Côtes de Genèveor Geneva Stripes (term damaskeening is used in America) is a decorative patterning of regular parallel strokes that give a ribbed aspect to the surface of given parts of a watch, often the bars and bridges of a movement.

COUNTERFEIT PARTS

Any aftermarket parts that bear illegal, fake or otherwise non-authentic trademarks, logos or hallmarks are counterfeit parts used to make the watch or its parts appear as authentic.

CROWN

A Crown, also known as a winder or winding stem, is the grooved button on the outside of the watch case used for setting the hands, and day and date if applicable. It is also used for winding the mainspring of a mechanical watch.

CROWN GUARDS 

Crown guards are two protrusions on a watch case on both sides of the crown that protect it from damage.

CRYSTAL

A crystal is a clear glass, plastic, mineral or sapphire crystal cover protecting the dial.

CUSHION CASE

A cushion case is a squared shape watch case with rounder edges.

CYCLOPS

A cyclops is a glass bubble positioned over the date aperture of the watch dial. It serves to magnify the date to be more easily read. It was first patented on May 1st 1952 and publicly released on the Rolex Datejust at the Basel fair in 1954.

DAY-DATE

A Day-date is a watch model showing both the current day of the week and date of the month.

DEPLOYMENT (DEPLOYANT) BUCKLE

A deployment/deployant buckle attaches to either side of the strap and is expandable so that the watch can be slipped on and snapped shut on the wrist. Once set to the correct size it needs not be adjusted again, which reduces its wear and prolongs its life. As an addition, this type of a buckle prevents the watch from slipping off one’s hand and falling down while putting the watch on or when taking it off.

DIAL

Dial is a face of a watch where its hour markers (or indices) and hands are placed. On date and day-date models’ dials an aperture is cut to allow the number wheels to be read.

DIVERS’ EXTENSION

A divers’ extension is a special extension within a diver watch bracelet allowing the bracelet to be lengthened in order to fit over a wet suit.

DIVER WATCH

Diver watches are waterproof for over 20 Atm and always have screwed crowns and screwed-in backs. They feature a stronger watch case and a thicker crystal to help resist the water pressure. A bezel on a diver watch rotates only one way so that a diver cannot adjust the time to their disadvantage by accident.

DOME

A dome is a nickname to the concave shaped glass given to it by Rolex collectors.

DOUBLE CHRONOGRAPH

A double chronograph, also known as a rattrapante or a split-second chronograph, is a watch that has two separate stopwatch mechanisms. A watch with a double chronograph has two seconds hands and while one moves continuously, the other one can be stopped, started or reset to zero.

DOUBLE NAMED WATCHES

A double named watch is a watch that has more than one company’s name written on its dial (i.e. the manufacturer and retailer: Rolex and Tiffany&Co).

DOUBLE QUICK SET

A double quick set feature was introduced in the late 90s and allows both the day and the date functions to be set rapidly by turning the crown without having to rotate the hands over and over.

DOUBLE SWISS

Double Swiss is a double printing of the word SWISS at the 6 o’clock position (on dials circa 1960). Note that the second and the lower inscription is normally not visible fully until the dial is removed from the case.

DUAL TIME

A dual time watch shows local time and the time in at least one other time zone. It is usually displayed with a help of an additional hour hand that tracks time in a 24 hour mode. Other times, a watch would have a separate sub-dial showing the full clock in the additional time zone.

EAGLE BEAK

Sharp pointed crown guards reminiscent of an eagle’s beak are known as the “Eagle Beak”.

EBAUCHE

Ebauche is a movement without a mainspring and balance, usually built by ebauche manufacturers to be sold later. The missing mainspring and balance are added afterwards as a movement is being completed by a watch manufacturer that bought this “blank” movement.

ELAPSED TIME ROTATING BEZEL

To keep track of elapsed time while diving, an elapsed time graduated rotating bezel is often used on diver watches.

END PIECE

An end piece is a small piece of metal made to look like a bracelet link allowing the bracelet to be attached to the case using tiny spring bars.

EQUATION OF TIME (EOT)

An Equation Of Time complication indicates the difference between “true” and “mean” solar time, or that of nature and that of man. 

ESCAPE WHEEL

An escape wheel is the last gear in the train in a lever escapement but it doesn’t turn other gears. It has specially shaped teeth that are alternately locked and unlocked by the motion of the balance and lever to regulate the motion of the watch in a controlled manner.

ESCAPEMENT

An escapement is a device that transfers energy to the timekeeping element allowing the number of its oscillations to be counted. In other words, it regulates the motion of the watch and allows the power stored in the mainspring to be released through the gears in a regular consistent manner. An escapement consists of the anchor wheel, the anchor and a lever with a spiral spring.

EXCLAMATION POINT

An exclamation point ia a phosphorus marker positioned above the 6 o’clock index and shaped like an exclamation point. Appears on gilt dials from the 60s. Please see a photo reference here.

F.A.P.

Rolex is known to having supplied its chronographs to professionals from various fields, and as part of this type of an initiative made some watches specifically for the Peruvian Air Force or Fuerza Aerea del Peru (or F.A.P. for short) The watches have special engravings on the caseback and the serial number engraved on the inside of the caseback, are rare and valued by collectors.

FLIP LOCK CLASP

A flip lock clasp is an extra folding lock on the older Rolex sports and diver models’ bracelets added for extra protection against the clasp opening.

FLYBACK

A flyback chronograph is a complication watch that restarts the moment it is brought back to zero without the need to stop, reset and restart the watch. The function is particularly useful for pilots.

FOLDED BRACELET

A folded Rolex Oyster bracelet is their second Oyster bracelet model. There is a folded link visible on the side, hence the name.

FORNITURA

Original spare watch parts built by the parent company and replaced after the model is out of production are called fornitura. Typically they would be slightly different from the original parts.

FUNCTION

A function (aka a complication) is a term used to describe any additional task a wristwatch performs (beyond the basic time telling), such as date, day of the week, moonphase, perpetual calendars or stop/start chronograph functions.

G.M.T.

This is the local time at the original site of the Royal Observatory in Greenwich, England, which is located on the prime meridian (at zero degree longitude). This time is used as the basis for standard time in most countries in the world.

GAS ESCAPE VALVE

A gas escape valve (aka a helium escape/release valve) is a one-way valve used in some diver watches (e.g. Rolex Sea-Dweller). It provides functionality for divers operating at great depths for prolonged periods of time by releasing the helium, hydrogen and/or other gases trapped inside the watch case during decompression.

GAUSS

The gauss (named after mathematician and physicist Karl F. Gauss) is a centimeter-gram-second electromagnetic unit of magnetic flux density, equal to one maxwell per square centimeter. The Rolex Milgauss model is named this way because it can withstand a magnetic flux density of 1 000 gauss (mille is Latin for “thousand”).

GILT DIAL

A gilt dial features the gold leaf or gold paint covering underneath with the writing and minute markers cut out and shining through in what is called negative relief.

GOLD PLATED

Gold plating refers to a layer of gold electroplated to a base metal (most commonly silver).

GRANDE COMPLICATIONS

Some of the most complex mechanical watches feature an abundance of complications referred to as grande complications.

GUILLOCHE

In French, “guilloche” means “engine turned”. It is an engraving technique in which intricate repetitive patterns or desigs are mechanically etched into an underlying material. Guilloche is used in decoration of watch dials, rotors or case parts.

HACKING

The hacking feature introduced in the 70s lets the second hand to ‘stop dead’ when the winding crown is pulled out fully to set the time. This allows for an easier way to synchronize one or a few watches.

HAIRSPRING

Also referred to as the “balance spring”, hairspring controls the swing of the balance.

HALLMARK

A hallmark is a mark or stamp indicating the purity of a precios metal. In some countries, the hallmark is made up of several elements rather than just one. For example, additional elements could be a mark denoting the type of metal, the maker’s mark and the year of the marking.

HELIUM VALVE

A helium valve is used in diver watches. It provides functionality for profesional divers operating at great depths of the sea in a helium capsule/diving bells. The extreme pressure inside the capsules forces the helium molecules to penetrate into the watch, and when the divers ascend to the surface again the helium expands and a watch could explode. The helium valve allows the helium to be released as divers resurface and prevents a watch from exploading.

HONEYCOMB DIAL

A Rolex honeycomb dial has a honeycomb-like texture, hence the name.

HOROLOGY

Horology is the science of measuring time and the art of designing and constructing watches. Those interested in horology are referred to as horologists.

HOUR MARKER

An hour marker is a simple line design used on a watch instead of numerals to indicate the hour.

INTEGRATED BRACELET

An integrated bracelet is a watch bracelet that is incorporated into the design of the watch case.

LINEN-TEXTURED

Linen-textured decorative finishing is formed with fine crossing lines. The style is most commonly used on classic gold Rolex bracelets and cases.

LOLLYPOP

A seconds hand with an oversized glowing disk is nicknamed lollypop. Used on some of the Omega and Rolex sports models in the 50s-60s.

JEWEL BEARING

A jewel bearing is a machine element that constrains relative motion to desired motion and reduces friction between moving parts using jewels (usually synthetic sapphires or rubies). Jewels are set in the metal plates that support the gears, and a metal spindle turns in a jewel-lined pivot hole.

JUMP HOUR

A jump hour watch is a watch where the hour hand is replaced with an aperture, usually at the 12:00 position, that displays current time in a digit format from 1 to 12. Every hour the digit changes automatically when the minute hand passes the 60-minute mark.

KARAT

The karat (abbreviated “K” or “kt”) is a unit of purity for gold alloys. 24K gold is pure gold not mixed with other metals, 18K gold is 75% pure, 14K gold is 58.5% pure and so on.

LADY PRESIDENT

Lady President is a nickname given to the ladies’ Rolex Datejust watch with a President bracelet.

LEVER ESCAPEMENT

The lever escapement was invented by English horologist Thomas Mudge around 1755 and is currently used in almost all mechanical watches. It consists of an escape wheel, “lever” and a balance wheel. The lever is initiated by the balance wheel and locks and unlocks the escape wheel, transferring the power through the gear train in an even and controlled motion and moving the hands forward at a steady rate.

LUGS

A lug of a wristwatch is a protrusion on the case with the two pointed edges where the watch strap or bracelet is attached.

LUMINOUS

Luminous paint applied to watch hands and hour markers is a standard feature on many wristwatches. The paint illuminates in the dark making it posible to tell time in the absence of light.

MAINSPRING

A mainspring is the power source of a mechanical watch that drives the watch movement.

MANUAL WIND

A manual watch needs to be hand-wound periodically in order to wind the mainspring and power the watch until the next winding.

MARK (MK)

A Mark (i.g. 1, 2, 3), commonly abbreviated as “MK”, indicates a series of a given model’s dial, pushers or other parts of a watch.

MECHANICAL

A mechanical watch is driven by a mainspring and not by a battery.

MERCEDES HANDS

Hour hands with a round emblem resembling that of the Mercedes Benz logo are sometimes referred to as the “Mercedes hands”.

METERS FIRST

Rolex Submariner dials that indicate the depth first in meters and then in feet are called Meters First dials.

METROPOLITAN

A metropolitan is a term used to refer to a sectored dial.

MID-SIZED WATCH

A mid-sized watch is smaller than a regular men’s watch and measures at approximately 34-36 mm (versus the regular measuring at 37-39 mm and sports models at 40-42 mm).

MINUTE REPEATER

A minute repeater is a complication in a mechanical watch that chimes the time down to the minute on demand at the press of a button. It uses separate tones for hours, quarter hours and minutes.

MONOPUSHER CHRONOGRAPH

A monopusher chronographer is a stop watch operated by a single button that allows to start, stop and reset the watch.

MOON PHASE

A moon phase complication indicates the current phase of the moon.

MOTHER OF PEARL

Mother of pearl is the internal layer of certain mollusk shells that is used as a jewelry component. In horology, it is used to decorate watch dials.

MOVEMENT

A movement is the mechanism of a timepiece.

NATO STRAP

A nato strap is a military style watch band made of nylon or waterproof canvas in a variety of colors.

NIPPLE DIAL

A so called Nipple Dial features slightly protruding applied round-shaped hour markers.

NUMERALS

Arabic and Roman numerals are the symbols used to represent numeric information on a dial and thus to tell time.

OPEN MINUTE DIAL

An open minute dial features disconnected minute graduations.

OVETTO

The nickname Ovetto (Italian for “little egg”) was given to the Rolex Bubbleback models because of the shape of their cases.

OYSTER

The Oyster case was invented by Rolex in 1926 and was the first waterproof case for a wristwatch.

PATENTED

A “patented” marking indicates that a patent has been issued.

PAT. PEND.

The abbreviation “pat. pend.” or “patent pending” marking indicates that a patent application has been filed.

PATINA

Patina is a layer of naturally formed chemical compounds or changes in texture or fading/darkening on a surface that develops with age and/or exposure.

PEPSI BEZEL

A “Pepsi bezel” refers to Rolex GMT Master’s red and blue bezel insert. The name is inspired by the soft drink producer’s brand color theme.

PERPETUAL MOVEMENT

A perpetual movement is a self-winding/automatic movement.

PERPETUAL CALENDAR

A perpetual calendar complication correctly displays the date on the watch, taking into account the different lengths of the months and leap days.

PERLON STRAP

A perlon strap is a braided watch band made of synthetic polyamide fibers similar to nylon.

PIE-PAN DIAL

A Pie-Pan dial is one that has a raised flat center and the hour/minute markers ring placed slightly below that raised center, as if repeating the shape of a pie pan.

POWER RESERVE

A mechanical watch is operated by automatic or manual winding and the term “power reserve” refers to how long a watch can function when not worn (automatic winding movement) or how much time is left until the watch needs winding (manual winding movement).

POWER RESERVE INDICATOR

Power Reserve Indicator is a mechanical watch complication designed to show the amount of remaining stored energy.

PRESIDENT

The term “President” is commonly used to refer to Rolex Day-Date, although officially, it only refers to a bracelet style. The nickname stuck after one of the Day-Dates was given to then President of the USA Dwight D. Eisenhower to celebrate his re-election and many of his succesors were seen wearing this model too.

PULSOMETER

A pulsometer is a scaling on a dial that lets you measure heart rate and breathing.

PUSHERS

Pushers are the buttons on the case of a chronograph that are used to stop and start a stopwatch. Ocassionally, they might perform other functions, too.

QUARTZ MOVEMENT

Quartz watches use a small energy cell or a battery that replaces a mainspring as the power source. The electronic oscilliator in a quartz movement is regulated by a quartz crystal to keep time.

QUICK SET

A quick set feature was introduced in the late 70s and allows both the date function to be set rapidly by turning the crown without having to rotate the hands over and over.

RADIAL DIAL

A radial dial features longer minute markers and shorter palet hour markers.

RAIL DIAL

A rail dial is a Rolex dial that has the “superlative chronometer” and “oficially certified” inscriptions centered in a way that the space between the two words in one inscription matches the position of that of the other one below it, creating a clear straight “track” instead of a zigzag one. Please see a photo reference here.

RATTRAPANTE

A rattrapante chronograph, also known as a double or a split-second chronograph, is a watch that has two separate stopwatch mechanisms. A watch with a rattrapante chronograph has two seconds hands and while one moves continuously, the other one can be stopped, started or reset to zero.

REFERENCE

A watch reference number identifies a model of a watch.

REGISTERS

The term “registers” refers to the extra function dials on the dial of a chronograph watch.

REGULATOR/REGULATEUR

A regulator or a regulateur watch displays hours, minutes and seconds on separate dials which allows for more accurate time telling.

REPEATER

A repeater is a complication in a mechanical watch that chimes current time on demand at the press of a button.

RETROGRADE

A retrograde display is one where a hand moves along an arc to indicate the time. When the hand gets to the end, it jumps back to the beginning of the arc.

RHODIUM PLATING

Rhodium is a rare silvery-white metal belonging to the platinum group. Rhodium plating is a process in which a thin layer of rhodium is applied over silver, platinum or white gold to increase durability and give a metal (white godl specifically) shine and color.

RIVET BRACELET 

A river bracelet (or a riveted bracelet) is an expandable bracelet used by Rolex in the 50s and 60s.

ROLESIUM

Rolesium is a combination of 904L stainless steel and platinum patented by Rolex in 1932.

ROLESOR

Rolesor is a combination of stainless steel and gold patented by Rolex in 1933.

ROMAN-ARABIC DIAL

A Roman-Arabic dial (aka California dial) is a dial featuring a combination of both Roman (10 o’clock to 2 o’clock) and Arabic numerals (4 o’clock to 8 o’clock) with 3, 6, and 9 sometimes being replaced with a dash instead of a numeral and 12 featuring an inverted triangle in its place.

ROTOR

A rotor is a rotating weight used in automatic movement watches. It swings back and forth with the movement of the wearer’s hand and winds the mainspring.

ROULETTE DATE WHEEL

A roulette date wheel is a date wheel that showcases the current date in alternating red and black colors (for even and odd numbers respectively).

SAPPHIRE CRYSTAL

Sapphire crystal was first introduced in 1970 and is now used in most watches. This synthetic glass is resistant to scratches but cannot be polished.

SCREW DOWN CROWN

A screw down crown ensures the watch’s water resistance by creating a seal when the case locks with the crown’s internal threads and gaskets.

SECOND TIME ZONE INDICATOR

A second time zone indicator can be featured as an additional dial on a watch or in a bezel format allowing the wearer to keep track of time in two different time zones of his/her choice.

SELF WINDING

A self winding watch is wound by the movement of a wearer’s wrist. Such movement causes a rotor or a balance weight inside the watch to rotate back and forth. The weight is connected to the barrel arbor (which is hooked to the mainspring) by a gear train, thus winding it and keeping it in constant tension.

SERIAL NUMBER

A serial number is a unique number of a watch given to it by a manufacturer. It is usually engraved between the lugs and/or on the inside or outside of the case back.

SIGMA DIAL

The term sigma dial refers to a Rolex watch dial featuring a symbol reminiscent of the Greek alphabet letter sigma “σ” in place of the O’s in the “O T SWISS T O” inscription on the bottom of the dial at 6 o’clock. Please see a photo reference here.

SHOCK ABSORBER

A shock absorber is a system used in mechanical watches to protect their delicate parts (like balance staff and balance pivots) against possible damage caused by a “shock” of a watch being bumped against something or dropped.

SKELETON WATCH

A skeleton watch is one, where the moving parts are visible through either the front or back of a watch, or through a cut on the dial.

SKELETON HANDS

Skeleton hands are watch hands with a cut out center and solid outlines.

SPLIT-SECOND CHRONOGRAPH

A split-second chronograph, also known as a rattrapante or a double chronograph, is a watch that has two separate stopwatch mechanisms. A watch with a split-second chronograph has two seconds hands and while one moves continuously, the other one can be stopped, started or reset to zero.

SPRING BAR

A spring bar is a small pin connecting a watch bracelet onto the case between the lugs.

SUBSIDIARY SECONDS

Subsidiary seconds is a smaller seconds subdial usually positioned at 6 o’clock.

SUPER BALANCE

Rolex developed and patented the Super Balance in 1935. This streamlined balance wheel improved the functioning of the Auto-Rotor movement.

SWEEPING MOVEMENT

The term sweeping movement refers to a second hand that ticks multiple times per second (as opposed to once per second) giving an illusion of a smooth continuous movement.

TACHYMETER

A tachymeter scale is inscribed on a chronograph’s bezel and is used to calculate speed based on travel time or measure distance based on speed.

The TANK 

The Tank (aka Cartier Tank) is a line of rectangular watches designed and made by Cartier. The design was inspired by the lines and proportions of the tanks used during the World War I, hence the name.

TELEMETER

A telemeter scale is inscribed on a chronograph’s bezel and is used to calculate the approximate distance between the user and an event that can be both seen and heard.

THUNDERBIRD BEZEL

A Thunderbird bezel is a bezel fit to Rolex Datejust Turn-O-Graphs developed for and used by the U.S. Air Force Thunderbirds. Please see a photo reference here.

TONNUEAU CASE

A tonnueau case is a squared case with rounded sides reminiscent of a shape of a barrel.

TOOL WATCH

A tool watch is one that is first of all designed for a specific purpose (e.i. diving) and not just as a decorative piece.

TOURBILLON

A tourbillon is an addition to a watch escapament that was developed and patented by Abraham-Louis Breguet in 1801. It aims to counter the effects of gravity by placing the escapament and balance wheel in a rotating cage. This is done to negate the effect of gravity when the watch is positioned in a certain way for a prolonged period of time.

TRIDOR

A Tridor is a rare Rolex bracelet used on some of the Day-date models and made using three shades of gold: white, yellow and pink.

TRIPLOCK

A Triplock winding crown system by Rolex features a triple seal against water and dust.

TRITIUM

Tritium is a luminous material that was used on the hands and hour markers of a watch making it posible to tell time in the absence of light. This radioactive material was discontinued in favor of the safer one.

TROPICAL DIAL

A tropical dial is one that turned brown with age.

TWINLOCK

A Twinlock Rolex winding crown system features a double seal against water and dust.

TWO-TONE 

The term “two-tone” refers to a watch made of two different metals, most commonly stainless steel and yellow gold.

UNDERLINE

Underline is a silver underscore under the “Rolex Cosmograph” inscription on early Daytona models circa 1963. It is believed to indicate the use of tritium in place of radioactive radium.

UNI-DIRECTIONAL ROTATING BEZEL

A uni-directional rotating bezel is one that can only be rotated in one direction – counterclockwise.

WORLD TIME COMPLICATION

A world time complication is one that tells time in all 24 time zones around the world. The names of major cities represting each time zone are printed on the dial of a watch with this complication.