The viper's head was the official Besançon Observatory hallmark, acknowledging the fact that the watch took part in one of their timing contests.Results of the Bulletin de Marche: Maximum average variation + 2.01 Variation between horizontal and vertical positions - 0.82 Average daily error ± 0.218 Average positional error ± 68 Temperature compensation error for 1oC + 0.09 Restart - 1.96It is very rare to find a watch accompanied by its original papers, box and medal.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 two other famous alloys invented by Guillaume, 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 ap-proximately a linear function of temprature, while the change of rate caused by change in elasticity of a balance spring is approxi-mately a quadratic function. Thus, it equals zero at only two tem-peratures, causing secondary error. Countless attempts were made to eliminate Middle Temperature Error, usually by means of aux-iliary 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 brass in bimetallic lamina, mkes its expansion close to quadratic. Balances with bi-metallic rims made of anibal and brass are usually called Guillaume balances, or, as their inventor called them, integral balances. When combined with special balance springs, they exhibit remarkable temperature stability, on occasion not exceeding 1/50 second per day at 1oC.