ACRYLIC CRYSTAL: First introduced in the 1920s, these are also called plastic crystals.
AFTERMARKET ROLEX PARTS: Any non-genuine, or non-Rolex made parts that DO NOT bear counterfeit Roiex trademarks, logos or hallmarks.
APERTURE: Small openings on the dials of some watches. It is inside these apertures where indications are ;ven (e.g. numbered date, hour or day of the week).
ARABIC NUMERALS: Figures on a dial representing the hours (i.e. 1, 2, 3, 4), as opposed to Roman Numerals i.e. I, II, Ill, I\l).
ARBOR: The shaft or axle that a gear rides on. At each end is a narrower segment called the “pivot”
ATMOSPHERE: Used as a measure of the watertightness of a watch case. One atmosphere equals average a’ pressure at sea level, approximately 14.7 pounds per square inch. Since one atmosphere equals 33.90 eet of water, a 3 ATM water resistant watch is considered water resistant to approximately 100 feet.
AUTOMATIC WINDING (also Self Winding): An automatic watch is wound by the movement of the wearer’s .‘. s. This movement causes a weight inside the watch to rotate backwards and forwards. The weight is conected by a gear train to the barrel arbor, which is hooked to the mainspring, thus winding it and keeping it in :onstant tension.
AUTO ROTOR: Rolex patented perpetual movement invented by Emil Borer in 1931.
BAGUETTE: A ladies style watch (or movement) featuring a thin rectangular or oval shape.
BAKELITE: The transparent acrylic material used on the bezel of early model GMT-Masters in 1954.
BALANCE: The governor or controller of a watch; it consists of a metal wheel, now commonly made of Invar, special steel resistant to changes in dimension due to fluctuations of heat or humidity and usually is mounted
•‘.ith a hairspring also of Invar or a similar alloy.
BALANCE SPRING: Also referred to as the “hair spring”, this spring controls the swing of the balance.
BALANCE WHEEL: A portion of the escapement, which divides time into equal sections.
BARK FINISH: The finish on some bracelet links that resembles the bark of a tree.
BARREL: Often called the “mainspring barrel” this is a circular box, often connected to a gear, which holds :- mainspring, which drives the watch.
BEAT: Measured in either Beats Per Hour (BPH) or Beats Per Second (BPS), this is the number of times per
– 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: The ring around the crystal on the top portion of a watch. Often, the bezel is made from varying matenals (i.e. stainless steel or gold) within a watch line—See also rotating bezel, bi-directional rotating bezel and uni-directional rotating bezel.
BI-DIRECTIONAL ROTATING BEZEL: A bezel which can be rotated either clockwise or counterclockwise, and is used for making calculations.
BOY’S SIZE WATCH: 2mm smaller than that of a standard men’s size watch.

CROWN GUARDS (also Shoulders): Protective rails protruding from the watch’s case on either side of the :c.n for the purpose of protecting it from damage.
CUSHION CASE: Squared shape with rounder edges, used on older model watch cases.
CYCLOPS: Glass bubble positioned over the date aperture for the purpose of magnifying the date to be more easily read. First patented on May 1, 1952, and publicly released on the Datejust at the Basel fair in 1954.
DCI (Decompression Illness): A condition, especially in divers, caused by the release of nitrogen bubbles in me tissue and blood upon too rapid a return from high pressure to atmospheric pressure—characterized by ains in the joints, cramps, paralysis and possibly death. This condition is often referred to as ‘the bends”
DIAL: This is the face of the watch, on which the hour markers (or indices) and hands are attached. On date and day-date models, an aperture is cut in the dial to allow the number wheels to be read.
DIVERS’ EXTENSION: Used on divers’ watches, a “hinged” extension within the watch’s bracelet, which alows the bracelet to be lengthened so as to fit over a wet suit.
DOUBLE QUICK SET: Introduced in late 1990, this feature allows both the day and the date to be rapidly set ia the winding crown—See also quick set.
DOUBLE NAMED WATCHES (also Co-Branded): Refers to watches that bear more than one company name on the dial (ie. the manufacturer and retailer).
EBAUCHE: A movement blank. Typically, an ebauche does not include a mainspring or balance. These items are added as a movement is completed.
ELAPSED TIME ROTATING BEZEL: A graduated rotating bezel often found on divers’ models, used to keep :acK of elapsed time while diving.
END PIECE: The small (usually hollow) piece of metal, crafted to look like a bracelet link, which allows the :-acelet to be attached to the case via tiny spring bars.
ESCAPEMENT: Allows the power stored in the mainspring to be released through the gears in a regular and controlled manner—See also lever escapement.
ESCAPE WHEEL: In a lever escapement, this is the last gear in the train, but does not turn other gears. Instead it has specially shaped teeth that are alternately locked and unlocked by the motion of the balance and ever to regulate the motion of the watch in a controlled manner.
FLIP LOCK CLASP: Clasp used on special Oyster bracelets, whereas the buckle utilizes a ‘flip-lock’ safety clasp to help prevent accidental loss. These are often found on divers’ models (i.e. Submariner, Sea-Dweller).
GAS ESCAPE VALVE: A one-way valve used in the Sea-Dweller, by which the helium particles are allowed to escape from the watch’s case during decompression. Sometimes called a helium escape valve.
GAUSS: The centimeter-gram-second electromagnetic unit of magnetic flux density, equal to one maxwell per square centimeter. [After Karl F. Gauss (1777-1855).] – The American Heritage Dictionary, Second College Edition. Copyright © 1985 by Houghton Mifflin Company. All rights reserved. Please Note: The Rolex Milgauss gets part of its name from this term (i.e. Mill-Gauss).
GILT (or Gild): Gold plated, or having a gold color or hue.
G.M.T: Abbreviation for Greenwich mean time. Time is calculated from the naval observatory at Greenwich, England, which is located at zero degrees longitude.
GUILLOCHE: French term meaning “engine-turned”.
HACKING: Introduced around 1972, this feature causes the second hand to ‘stop dead’ when the winding crown is pulled out fully to set the time, thus allowing for more easily synchronizing of one or more watches.
HALLMARK: A mark or stamp indicating the purity of a metal, or the date, and/or country of import.
HAIRSPRING: See Balance Spring.
HERMETIC: Completely sealed, especially against the escape or entry of air and/or dust.
HONEYCOMB DIAL: A Rolex dial model featuring a honeycomb-like texture—See also guilloché.
HOROLOGY: 1—The science of measuring time. 2—The art of making timepieces.
HUNTERCASE: A case used on pocket watches and even some early wrist watches, whereas the front and
back are protected by hinged covers, which are usually spring loaded.
INCABLOC: The best known of the various competing shock absorbers for watches, it is manufactured by
Potescap SA and considered an industry standard.
INDICES: Another term for the hour markers on a watch’s dial.
JEWEL: A precious stone (usually a synthetic sapphire or ruby) that is used as a bearing for watch gears to reduce friction. The top of the jewel has a depression to hold oil. Jewels are set in the metal plates that support the gears. The pivot (the tip of the gear arbor) goes though a hole in the jewel.
JUMP HOUR: From Heures Sautantes, a watch were the hour hand is replaced with a tiny aperture at the 12 o’clock position. Through this window one could view a miniature wheel displaying the numbers 1 thru 12. When the minute hand passed the 60-minute mark, the wheel would turn, thus the hour marker ‘jumping’ into place at the start of each hour.
LADY PRESIDENT: This nickname is often used to refer to the ladies’ Rolex Datejust fitted with a President bracelet.
LEVERESCAPEMENT: Invented by Thomas Mudge in 1759, it subsequently replaced all other types of watch
• escapements, and is currently the only type of escapement manufactured for watches. Consisting of an escape wheel, “lever” and a balance wheel, the lever, when initiated by the balance wheel, locks and unlocks the
• escape wheel, thus transferring power through the gear train in an even and controlled motion.
LIGNE: A pre-metric system of measurement still used in Switzerland to measure watch movements. One ligne (“) is approximately 2.256 mm.
LOUPE: Often called a jewelers’ or magnifier loupe. It is used to inspect fine detailed markings, and very small parts.
LUGS: The two pointed edges on either end of the case, by which the bracelet is attached to the case through the end pieces. These are often called the ‘horns’.
aLUMINOVA: Organic, non-radioactive, luminous material now used on the hands and hour markers of a watch. It replaced the older (and more dangerous) radioactive material Tritium around 1998.
MAINSPRING: The principal spring of a watch that supplies the force of motion to the gear trains.
MECHANICAL: Movement used on traditional timepieces, whereas the watch uses a main spring for its power source and must be hand wound.
MERCEDES HANDS: Nickname used to describe a style of hands used on some sports model watches. The arne comes from the hour hand which features a round emblem which resembles the logo of the German
automobile manufacturer Mercedes Benz. Rolex refers to these hands as skelette or skeleton hands.
MICRO-STELLA: Tiny screws used for adjustment of the balance.
MID-SIZED WATCHES: Refers to Rolex models that are 80% of the size of a standard men’s watch.
MILLED EDGE: Having a grooved or coined edge. First used on watch cases by the Dennison Watch Case cD-npany in the early 1900s, and is still featured on the back of all Rolex Oyster cases.
MOON PHASE: A type of dial showing the changes in the moon’s phases, or lunar cycles.
MOVEMENT: The machinery of any time piece.
NITROGEN NARCOSIS: This alcohol-like effect is often called ‘rapture of the deep’, whereas the body absorbs a toxic level of nitrogen, which in some cases can cause death.
OCTAGON CASE: A watch case having eight sides, shaped similar to that of a stop-sign.
OFFICIALLY CERTIFIED CHRONOMETER: Around 1949, Rolex introduced this wording on the dials of their chronometer-rated models.
OVETTONE (or Ovetto, or Ovitone): Italian for ‘little egg’, this nickname was associated with the Bubbleback
—Ddels due to their rounded shape.
PEDOMETER: The first self-winding pocket watch design, invented by Abraham-Louis Perrelet in 1770, thus named after the source of its power (i.e. a weighted lever that jerks as a man walks).
PRECISION: Term used by Rolex to describe their watch movements which had not received a timing certificate. thus were not rated as chronometers.
PERPETUAL MOVEMENT: Another term for an automatic or self-winding movement with a winding rotor that travels a full 360 degrees.
PIVOT: The turned down part of an arbor. This part commonly projects through the hole in watch jewels.
PLATE: The portion of the movement which supports the bridges and other plates.
PRESIDENT (also Presidential): This nickname is often used to describe the Rolex Day-Date models, since one was given to then President Dwight D. Eisenhower in 1956, to celebrate his re-election and nearly every Desident since Franklin D. Roosevelt has worn one. However, the name ‘President’ is officially only used to describe the bracelet style featured on the Day-Date model.
QUARTZ MOVEMENT: Quartz watches use a tiny energy cell (or battery) to replace the mainspring as the :ower source. The oscillating mass is replaced by a tiny piece of shaped quartz crystal, which is tuned to a requency of 32,768 Hz (cycles per second)—this is often called the piezoelectric effect and is similar to that of a tuning fork. A system of integrated circuits then divides the frequency into one-second pulses to drive a tiny rotor. which in turn drives the hands.
QUICK SET: Introduced in late 1970, this feature allows the date to be rapidly set via the winding crown, with. t having the hour hand pass over the ‘midnight’ position—See also double quick set.
RADIUM: Radioactive luminous material first used on the hands of watches around 1913. This material was subsequently replaced by Tritium around 1950.
REFERENCE NUMBER: The case or model number of a watch, usually engraved between the lugs, and/or inside/outside the case back.
REGISTERS: Term used to describe the subsidiary ‘extra-function’ dials positioned on the face of a chronograph watch.
ROLESIUM: A Rolex term used to describe the case metal mixture of stainless steel and platinum, trademarked on May 21, 1932. This configuration is currently seen on the Rolex Yacht-Master.
ROLLESOR: A Rolex term used to describe the case metal mixture of stainless steel and gold, trademarked on April 1, 1933.
ROMAN-ARABIC DIAL: See also California Dial.
ROTATING BEZEL: Often used on sports watches like divers’ or aviator models, it is used to perform an additional function, such as checking decompression times, or telling the time in different time-zones—See also bidirectional rotating bezel and uni-directional rotating bezel.
ROTOR: The oscillating weight used in an automatic movement.
RUBY: See also Jewel.
SAPPHIRE CRYSTAL: First introduced in 1970, on the Ro/ex Quartz, these synthetic crystals are now used in most watches, due to the fact that they are highly scratch resistant.
SELF WINDING: See also Automatic Winding.
SERIAL NUMBER: An identification number of a watch, usually engraved between the lugs, and/or inside/ outside the case back. This number can often be used to date the production of the watch.
SHOCK ABSORBER: A system where the jewels on the balance staff are spring mounted, thereby protecting the balance staff from damage, in the event that the watch is dropped.
SKELETON HANDS (or Skellete): Term used by Rolex to describe the hands on a watch that are ‘cut-out’ so they only feature an outline of the hands. Some of these hands are nicknamed Mercedes-style. SKELETON CASE: Also known as a ‘clear back’ model. It features a transparent front or back, thus permitting a view of the internal workings of the watch.
SPELEOLOGY: The study and exploration of caves. It was for these ‘cave dwellers’ (or speleologists) that the Rolex Explorer II was designed, whereby one could distinguish day from night with the use of a special 24- hour hand and bezel.
SPRING BAR: A small spring-loaded pushpin, which passes through the end piece into either side of the lugs, thus holding the bracelet onto the case.
SUBSIDIARY SECONDS (or Sunk Seconds): The small seconds dial, usually positioned at the 6 o’clock and is sunken so as not to impede the hour and minute hand.
SUPER BALANCE: Balance wheel design for the Auto Rotor Perpetual movement, patented by Rolex in 1935.
SUPERLATIVE CHRONOMETER OFFICIALLY CERTIFIED: Starting in 1957, Rolex introduced this wording to replace ‘Officially Certified Chronometer’ on the dials of their chronometer-rated models and it is still used to day.
SWEEPING MOVEMENT: Also known as the ‘step’ or ‘action’. Sweep refers to the movement of the second
– 2 quickly ‘ticking’ at approximately 5-8 times per second, thus giving the illusion of sweeping.
TACHYMETER (or Tachometer): A special scale printed on the outside of a chronograph, used to calculate :e average speed traveled over a measured distance. Frequently used in auto racing to determine ‘lap times’.
TELEMETER: A special scale printed on the outside of a chronograph, used to determine the distance of an DDect from the wearer by measuring how long it takes sound to travel that distance.
THUNDERBIRD BEZEL: Also called the Turn-O-Graph bezel in the U.K., thus named after the Turn-O-Graph
•.a:c- where it was first introduced. The bezel is now fitted to select Rolex Datejust models.
TOOL WATCH: This concept refers to watches created for use in specific sports or professional activities.
TONNUEAU CASE: Barrel-shaped case, whereas the ends are squared and the sides bow out in a rounded :D9vex shape.
TRAVEL CLOCK: Also called portfolio or purse watches. This refers to early covered, folding or protected 2 DK5. some of which were carried in women’s purses around the early 1 900s.
TRIPLOCK: Rolex screw-down crown, which features a triple seal against water and dust. First patented on .uIy 22, 1952, it features the Rolex crown underscored with three ‘dots’.
TRITILIM: Luminous material used on the hands and hour markers of a watch since the 1950s. This radioactive material was discontinued by Rolex around 1998, in favor of a safer material LumiNova. Modern watches DOntaining Tritium will be marked “T”, “T 25” , or “T<25” on the bottom of the dial. (Please Note: The radiation content is extremely small and is not a direct hazard to the wearer.)
TWIN LOCK: Rolex screw-down crown, which features a twin seal against water and dust. First patented on Apnt 20, 1953, it features the Rolex crown underscored with a single horizontal ‘line’.
TWO-TONE (also 2-tone or tu-tone): Refers to a watch case featuring two different metals (e.g. stainless steel and yellow gold).
UNI-DIRECTIONAL ROTATING BEZEL: Introduced in the 1980s, this elapse time bezel is often found on Dyers models, and only moves in the counterclockwise direction. Thus, protecting the diver from an erroneous (and potentially dangerous) reading when measuring decompression times, since any accidental move‘ent could only err on the side of safety.
WINDING STEM: Shaft on which the crown is fixed on an end.

Information found from “The Rolex Report”, revised and expanded 4th edition by John E. Brozek.