The Mondani Collection of Rolex Wrist...

Geneva, May 14, 2006

LOT 815

"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.

CHF 16,000 - 20,000

EUR 10,000 - 13,000 / USD 12,000 - 15,000

Sold: CHF 18,880

C. Four-body, "bassine", polished, hinged back with engraved monogram. Hinged gold cuvette with engraved presentation inscription. D. 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. M. 42 mm (19'''),"extra", "faussescôtes" decoration, wolf's tooth winding geared to an extra wheel operating the power reserve indicator, 21 jewels, counterpoised straight line lever escapement, Guillaume balance with gold temperature screws and platinum mean time screws, eight adjustments, blued steel Breguet balance spring, swan-neck micrometer regulator, diamond endstone. Dial, case, cuvette, and movement signed, movement numbered twice. Diam. 50 mm.


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Grading System
Grade: AAA

Excellent
Case: 3

Good
Movement: 3*

Good

Overhaul recommended, at buyer's expense
Dial: 3-01

Good

HANDS Original

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.