Important Collectors’ Wristwatches, P...

Geneva, Mandarin Oriental Hotel Du Rhône, May 13, 2007

LOT 270

?Chronometre ? Bulletin 1ère Classe with Honorable Mention? Vacheron & Constantin, Genève, ?Chronomètre ? Bulletin de 1ere Classe aux Observatoires de Geneve et Teddington?, No. 342901, case No. 246308. Movement made in 1916. Sold in 1926. Extremely fine and rare, hunting-cased, keyless, 18K yellow gold pocket lever chronometer with Guillaume balance, submitted for trial at the Geneva Observatory in 1920, regulated by A. Favre-Rochat, achieving 723 points and honorable mention. Accompanied by copies of the Geneva Observatory rating details.

CHF 20,000 - 30,000

EUR 12,000 - 20,000 / USD 16,000 - 25,000

C. Four-body, ?bassine?, solid, polished, the interior of the back with engraved dedication. Hinged gold cuvette with inscription. D. White enamel with dauphine numerals, outer minute track, subsidiary seconds dial. Gold ?spade? hands. M. 41 mm., Cal. 18???, rhodium-plated, 20 jewels, wolf?s tooth winding, counterpoised and calibrated straight-line lever escapement, anibalbrass Guillaume balance, gold meantime and temperature adjustment screws, blued steel Breguet balance spring, ?swanneck? micrometer regulator. Dial, case and movement signed. Diam. 51 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

The watch No. 342901 was regulated for the Geneva Observatory trials by A. Favre-Rochat and obtained 723 points out of a possible 1000. This watch came 18th overall out of the entire 43 classes on trial. The Guillaume Balance. (lot 270) 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. Around 1900 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 approximately a linear function of temperature, while the change of rate caused by change in elasticity of a balance spring is approximately a quadratic function. Thus, it equals zero at only two temperatures, causing secondary error. In 1899, Guillaume noted that steel with an addition of 44.4% nickel had a negative square coefficient of thermal expansion. Anibal, combined with brass in bimetallic laminae, makes expansion close to quadratic. Balances with bimetallic rims made of anibal and brass are usually called Guillaume balances. When combined with special balance springs as in the present watch, they exhibit remarkable temperature stability, on occasion not exceeding 1/50 second per day at 1oC