18,880 CHF
"Extra, Power Reserve" Patek Philippe & Cie, Genève, No. 162757, case No. 279012. Made in 1911 and sold to Wright, Kay & Co., Detroit, on 30th September 1913. Very fine and rare, 18K gold keyless pocket lever chronometer with "Extra" quality movement, power reserve and Guillaume balance, made for an Observatory trial. Accompanied by an Extract from the Archives. Four-body, "bassine", polished, hinged back with engraved monogram. Hinged gold cuvette with engraved presentation inscription. White enamel, black Breguet numerals, outer minute track and red Arabic five minute numerals, subsidiary seconds, power reserve sector below 12. Gold "Louis XV" hands. Notes Guillaume Balance In 1899, Dr. Charles Edouard 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, 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, on occasion not exceeding 1/50 second per day at 1ºC.
Auctioneer:
Antiquorum
Date:
2006-05-14
