Interested in knowing more about mechanical watches and terms? Here's a condensed glossary…
Accutron (tuning fork)
Accutron or 'tuning fork' movements are simple transistor oscillator circuit movement, driven a battery. This means they are considered to be the first electronic watches (see electric) and precursors to quartz watches. Instead of the ticking sound made by mechanical watches, Accutron have a faint, high pitched hum which comes from the vibrating tuning fork.
This term refers to a movement whose balance wheel spring is made of a nonmagnetic nickel alloy.
Automatic (aka self-winding)
An automatic watch uses the movement of the wearer’s body to tension the mainspring by means of a weighted rotor, which in turn winds the mainspring. A clutch mechanism regulates this action, so that regular wearing of such a watch makes the watch ‘perpetual.’
The metal ring surrounding the watch dial (or face).
Calibre (or Caliber)
The term is generally used to refer to the movement, its origins and/or its maker. Usually referred to by model or type number.
The outer ring on the dial face of the watch, bearing figures and minute marks. The hour figures are sometimes called chapters.
A chronometer movement is a highly precise and accurate watch movement. It must pass tests at different angles and temperatures in order to be officially certified by COSC, the Contrôle Officiel Suisse des Chronomètres.
A chronograph is a watch with the usual timing function, but with an additional module capable of stopwatch timing. As well as the usual dial markings, a chronograph is calibrated with markings traditionally known as tachy-télémetre, or pulsèmetre and which allow a user to calculate speed, pulse rate and distance.
A complication refers to any feature in a timepiece beyond the simple display of hours, minutes, and seconds. A grandes complications movement is a watch with several complications, such as tourbillon, perpetual calendar, moon phase, minute repeater or chronograph.
The button on the outside of the case that’s used to set the time and date. In a mechanical watch, the crown also winds the mainspring. In this case it is also called a ‘winding stem.’ A screw in (or screw down) crown can be used to make a watch more water resistant.
The transparent cover on a watch face made of glass crystal, synthetic sapphire or plastic.
A watch shaped like a cushion, with four convex sides.
An electric watch is a hybrid watch, having both a mechanical movement and an electrically driven and regulation system. It requires a battery to operate.
Engine-turned or guilloché
Delicate engraved patterns on metal watch components, including cases, dials, bezels and movements.
Frequency or beat rate
A typical watch of the early 20th century operated around 5 beats per second, or 18,000 vph (vibrations per hour, sometimes written as bph or beats per hour). In the late ‘40s, a number of watch manufacturers introduced movements with a beat rate of 6 bps, or 21,600 vph. With improvements in lubricants, beat rates have increased and 8 bps (28,800 vph) not uncommon, with some ‘hi-beat’ watches operating at 10 bps (36,000 vph). Argument rages amongst horologists, but it’s generally felt that higher beat rates can yield better accuracy.
Elegant decorative parallel waves carved on the exposed plates and bridges of the movement. Generally only found on high-end watches.
Gold-Filled, Rolled Gold Plate, and Gold Plating
Gold-Filled is a gold "sandwich" that has been produced by mechanically bonding a thin layer of gold to both sides of a thick base metal (usually brass) core. The sandwich of gold/brass/gold is rolled under very high pressure until bonded and to the desired thickness. Law requires that the gold content be no less than 1/20th (by weight) of the total metal content in order to be called gold-filled. It’s usually between 80-120 microns thick on watchcases.
Rolled Gold Plate (RGP) is similar to gold-filled, but with a thinner layer of gold required. Gold sandwiches less than 1/20th gold by weight that are produced by mechanical (pressing) means will generally be called rolled gold-plate or RGP. On watches, it’s usually between 20-40 microns thick.
Gold plated (plaque) items contain the least amount of gold. It differs from rolled gold plate because of the means of depositing or bonding the gold to the core base metal. Gold plate tends to refer to a thin layer of gold (usually less than 10-20 microns thick) applied through electrical/chemical deposition.
Greenwich Mean Time (GMT)
GMT is the abbreviation of Greenwich Mean Time, also known as Universal Time (UT).
This feature permits the second hand to be stopped and synchronized with another watch or time reference.
High-grade watches originally used genuine ruby bearing to reduce friction and wear. Synthetic rubies are more typical in today’s watches. A typical hand-wound movement today has around 17 jewels, sometimes far more in the case of an ultrathin or grandes complications.
Projections on a case to which the watchband or bracelet is attached.
Manual (aka hand-wound)
A manual winding watch requires daily winding to tension the mainspring.
A mechanical watch consists of a power mechanism, typically a winding mechanism and mainspring to store energy. The energy is transferred through a gear train and to speed regulator; these parts are as known the escapement and balance wheel. In turn, another set of gears turns the second, minute and hour hands. Mechanical watches can be either manually or automatically wound.
The inner mechanism or ‘works’ of a watch that keeps time and moves the watch's hands, calendar, etc.
A display in which the hands float on transparent discs and appear to float above the dial.
A moon phase watch works by rotating the moon disc in the movement to show lunar activity (new moon, last quarter and full moon) through a half round window on the dial.
Quartz watches can be analogue, digital or a combination of the two. They use battery power and quartz oscillation to keep time. Analogue quartz watches use battery power to make a quartz crystal oscillate and drive a step motor, which drives the gear train and turns the hands. In the case of a digital quartz watch, the crystal drives an LED or LCD display, with no step motor or hands.
Rhodium is an expensive silvery white noble metal. The process of rhodium plating is complicated, however it gives a hard, abrasion resistant and bright surface with greatly improved anticorrosion and chemical stability, therefore improving the reliability and service life of the watch.
The part of an automatic mechanical watch that winds the movement's mainspring. It is a weighted flat piece of metal, usually shaped like a semicircle that swivels on a pivot with the motion of the wearer's arm.
A crystal made of synthetic sapphire, a transparent, shatter-resistant, scratch-resistant substance.
Spring-loaded bars between the lugs on the case, used to attach a strap or metal bracelet to the case.
A rectangular watch designed by Louis Cartier. The bars along the sides of the watch were inspired by the tracks of tanks used in World War 1.
A watch shaped like a barrel, with two convex sides.
A rotary escapement regulator in mechanical watches. Being free from the influence of gravity, it can maintain the movement’s accuracy. In addition to all the functions of the escapement regulator or general mechanical watches, the tourbillon can continuously rotate in 360° around an axis to adjust the position of the system and offset the operation error caused by gravity.
For a watch to be considered waterproof, the case, crown and crystal must be waterproof and dustproof and maintain waterfastness at a specified depth under water.
Wind indicator or power reserve indicator
A sub dial, which shows how much power, is left in the mainspring, usually in terms of hours left to run.