85,100 HKD
Patek, Philippe & Cie, Genève, No. 170434, caseNo. 274716, made in 1912 and sold to US Naval Observatory on December 8, 1917.Very fine and rare silver keyless “EXTRA” adjusted deck watch with 36 hours power reserve indicator. Four-body, "bassine", polished, silver hinged cuvette. Notes Superbly adjusted Swiss watches of the period, and particularly those of Patek Philippe, were signed “EXTRA” or “SPECIAL”.Anibal (acier au nickel pour balanciers), an alloy invented by Dr. Charles Edouard Guillaume, exhibits unusual properties, both in terms of thermal expansion and changes in elasticity. These properties are very different from those of two other famous alloys invented byGuillaume, Invar and Elinvar. At the end of the 1800's, 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 modifications caused by change in elasticity of a balance spring are approximately a quadratic function. Thus, it equals zero at only two temperatures, causing secondary error. Countless attempts were made to elimnate 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, combined with brass in bimetallic lamina, makes its expansion close to quadratic. Balances with b
Auctioneer:
Antiquorum
Date:
2001-06-08
