28,750 CHF
Vacheron & Constantin, Genève, No. 444889, case No. 279516, made for the Wehrmacht, in 1937. Very fine and rare silver, keyless large deck and pocket chronometer with 32-hour power reserve indicator. Accompanied by the Extract from the Archives. Four-body, "bassine", polished, silver, hinged cuvette. Silver, champlevé Arabic numerals, outer minute divisions, up-and-down sector at 12 o’clock, subsidiary seconds. Blued steel "spade" hands. Notes Anibal (acier au nickel pour balanciers), an alloy invented by Dr. Charles Edouard Guillaume, exhibits unusual properties, both in terms of thermal expansion and in changes in elasticity. These properties are very different from those of the two other famous alloys invented by Guillaume, Invar and Elinvar. Around 1900 Guillaume attempted to eliminate the so-called Middle Temperature Error caused by the fact that the change of rate in a timekeeper with a steel-brass bimetallic balance is approximately a linear function of temperature, while the change of rate caused by change in elasticity of a balance spring is approximately a quadratic function. Thus, it equals zero at only two temperatures, causing secondary error. Countless attempts were made to eliminate Middle Temperature Error, usually by means of auxiliary compensation devices. In 1899, Guillaume noticed that steel with an addition of 44.4% nickel had a negative square coefficient of thermal expansion. This alloy, combined with rass in bimetallic lamina, makes its expan
Auctioneer:
Antiquorum
Date:
2004-04-24
