Swiss silver deck watch with Guillaume balance Circa 1945

Silver lever with centre seconds
–
A fine Swiss silver lever chronometer keyless deck watch with indirect centre seconds and Guillaume balance, circa 1939. A solid, polished case, screw-down back. White enamel dial with radial Roman numerals, outer Arabic minute and seconds ring with fifths of a second division and blued steel spade hands. A frosted and gilt movement, 18 jewels, straight-line lever escapement, Anibal-brass Guillaume balance, blued steel Breguet balance spring with a terminal curve, micrometric regulator. Dial, case and movement signed.
–
Diameter: 56 mm
–
Signed: Ulysse Nardin  Locle
–
In 1899, Dr Charles Edouard Guillaume noted that steel with an addition of 44.4% nickel had a negative square coefficient of thermal expansion. This alloy, combined with brass in a bimetallic lamina, makes its expansion close to quadratic. Balances with bimetallic rims made of anibal (Anibal, an alloy invented by Guillaume, stands for (Acier au NIckel pour BaLanciers) 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.