altimeter rotating bezel that measures the altitude.
atmosphere measurement of pressure. One atmosphere is equal to the pressure of one kilgram per square centimer. In watchmaking, an atmospheric measure is the amount of air pressure at sea level that a watch can withstand; 1 ATM = 33.9 feet of water, and 3 ATM = 100 feet.
balance mechanical watches are regulated with the balance and the balance-spring.
balance-spring also called the "hair spring." In a mechanical watch, attached to the balance and cock, and made of metal alloys. Its length determines the amount that the balance regularly oscillates; the shorter the spring the faster the watch runs.
barrel spring this spring’s tension controls the amount of energy transmitted to the movement. Hooked to the barrel and the arbor, when it is tensed it releases energy.
beat the number of times per second (beats per second (BPS) or per hour (BPH) that a balance wheel goes through a full arc of motion.
bevel furrow or groove cut at an angle that is either over or under, but not equal to, 90 degrees.
bezel groove or flange with a slanting surface designed to hold the beveled edge of an object; on watches, it is the ring that holds the crystal on the top of the watch.
blued screws steel screws which are hardened by being heated to high temperatures to relieve stress in the metal. The high temperature gives the steel a permanent blue.
bottom plate supporting the bridges, which are often on the top of the plate, the movement, the dial, and the holes where the jewels are inserted.
bridge balance cock attached to the bottom plate with pins.
galvanished finish the base metal of the movement is coated with a layer of gold or rhodium.
glucydur copper and glucinum stainless, non-magnetic alloy used in watchmaking for internal parts.
GMT Greenwich Mean Time, marking the middle of a solar day, is the time as measured from zero degrees latitude, in Greenwich, England.
going train made up of the going barrel, which drive the center wheel. The center wheel drives the third wheel, then the third wheel drives the second wheel. The second wheel drives the escapement wheel.
guilloche complex engraving that appears as lines or circles which interlock.
pallet a piece of the lever escapement, this is usually in the shape of a ship’s anchor.
perpetual calendar extremely elaborate complication that keeps track of the day, month, date, and sometimes even the moon phase, zodiac signs, decade, or century, and which adjusts for the length of the month and for leap years.
plate metal piece that holds up the bridges and other parts of the movement.
power-reserve the length of time beyond 24 hours that a watch will run without needing winding; ordinarily about 10 to 16 hours.
pre-owned watch watch that has been owned by another person.
pulsimeter a chronograph with an extra dial or timer that gives the rate of a pulse per minute.
tachometer / tachymeter counts the number of rotations to tell you how fast you travel over a measured distance.
tank rectangular watch case modeled on Cartier's WWI tank-inspired watch design.
telemeter stopwatch or chronograph complication with a scale that measures the distance of something from the wearer of the watch through the amount of time it takes for a sound to travel.
tonneau something in the shape of a barrel.
tourbillon "whirlwind," a complex mechanism requiring the highest watchmaking skills; consists of a mobile carriage carrying all the parts of the escapement. It is a regulating device which corrects for the gravity-caused differences in run time in a mechanical watch.
tritium luminous material that makes hour markers and/or hands easier to read in the dark; ideal for diving watches.