Watch Glossary and Terms with Images

Niello paste is applied over incised gold or silver then fired in the enamellist;s furnace. Excess niello is filed off and the su***ce smoothed. Polished niello cases were fashionable shortly before wristwatches were introduced.O ImagesObservatory chronometerA chronometer which has received an official rating certificate from an observatory.Official rating certificateA document, issued by an Observatory or an official ratings bureau, that certifies the quality of a watch which has proven, in trials, to meet with a given standard. Only a watch that has received an official rating certificate can be called a chronometer.Oil sinkA cavity in bearings for a drop of oil.Oscillating weight (Rotor)In a self-winding movement, a heavy metal disc that turns freely in both directions to wind the mainspring.OscillationWhen a pendulum or balance oscillates it moves between two extreme positions (A; and A;;). The movement from one of these positions to the other and back equals one oscillation. Marine chronometers with mechanical movements are mounted on gimbals so that they remain in the horizontal position is necessary for their precision.Middle (of watch-case)Middle part of the case, in which the movement is fitted.MovementAssembly consisting of the principal elements and mechanisms of a watch or clock: the winding and setting mechanism, the mainspring, the train, the escapement, the regulating elements. "Anatomically", the movement consists of the "ébauche", the regulating elements and the other components.N ImagesNickel silver (German silver)A silver-white alloy of copper, nickel and zinc developed in France circa 1820 by Maillot and Chorier from whom it takes its name.NielloAn enamel-like alloy of lead, copper, silver, sulphur and sal ammoniac (ammonium chloride).