Swiss silver deck watch with 36 hour power reserve Circa 1912

Silver keyless deck watch
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A very fine Swiss, silver deck and pocket extra adjusted lever chronometer with 36 hour power reserve indicator and Guillaume balance, circa 1912. Obtained the Geneva Observatory rating certificate on June 11, 1913, and sold it on December 8, 1917. Accompanied by the Extract from the Archives. A polished case, silver hinged cuvette. Heavy, solid silver dial, bold champlevé radial Roman numerals, outer champlevé minute track, an up and down sector at 12, and subsidiary seconds. Blued steel spade hands.
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Straight line calibrated lever escapement, 21 jewels, Anibal brass Guillaume balance with winged arms, gold temperature adjustment screws and platinum mean time ones, special alloy Breguet balance spring with Phillips’ inner and outer terminal curves, diamond endstone, swan-neck micrometric regulator, Patek Philippe & Cie. keyless winding (Swiss patent 2680, 27 September 1890), differential up and down mechanism. Dial, case and movement signed. Property of an American Gentleman.
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Diameter: 60 mm
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Signed: Patek Philippe & Cie  Genève
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Guillaume Balance 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 almost quadratic. Balances with bimetallic rims made of Anibal (an alloy invented by Guillaume: 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, on occasion not exceeding 1/50 second per day at 1oC. The present watches are exceptionally well made and adjusted for the Observatory Contests. Every detail, such as the special Guillaume balance with small wings at the arm for poising in the raw, before the screws are put in, which assures that temperature compensation adjustment will not affect poising, the superior polish of the steel parts, the olive jewel holes, and the very light undercut escape wheel with raised teeth, shows that these watches were very special ones.