Collector's Pocket Watches, Wristwatc...

New York, Grand Havana Room, Dec 06, 2000

LOT 272

Unsigned, Swiss, No. 101, circa 1860.Fine, 18K gold, keyless/keywound watch with highly unusual experimental constant force escapement.

USD 8,000 - 9,000

C. three body, solid, 'bassine et filets', engine turned back cover, gold, engine-turned cuvette. D. white enamel, Roman numerals, outer minute ring, subsidiary sunk seconds, snap-on fit, 'Spade' blued steel hands. M. 19''', gilded bar calibre, gold train, unusual escapement, combination of chronometer and lever with constant force action : the escape wheel consists of two wheels, the lower delivering the impulse, the upper for locking. The impulse is delivered to a roller mounted in jewells onpivoted detent. The roller turns freely to minimalize the friction, the locking spring is part of the detent mounted perpenduculary to it. On the detent there is a spiral spring that acts as a remontoire power. The end of the detent is fitted with a relatively larhe roller mounted in jewels whicjh rolls on a half-cylinder mounted on the balance staff, the energy in the constant force spring gives impulse to the balance via the roller when it rolls of the half-cylinder. The constant force springis mounted on an adjustable plate to control the energy needed to be delivered to the balance, in fact it is an amplitude adjustment, cut bimetallic compensation balance, flat balance spring. Index regulator with micrometric screw and adjustable key bracket, wolf-tooth winding wheels, winding only in one direction.Stamped ' FS ' inside back cover.Diam. 50 mm.


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Grading System
Grade: AAA

Excellent
Case: 3

Good
Movement: 3

Good
Dial: 3

Good

Notes

The escapement, which at first glance, can be mistaken for a combination of pivoted detent and lever escapement, is highly unusual, apparently experimental form of constant force, having solutions, such as the half-cylinder on the balance staff, never found in other forms of constant force devices. The stem, like in early watches can be turned in only one direction adding to the unusuality of the watch, the adjustable regulating key also confirms the experimental nature of the watch.