Important Watches, Collector's Wrist...

Hong Kong, Jun 08, 2001

LOT 441

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

C. Three body, massive, ?bassine et filets?, engine-turned back cover, gold, engine-turned cuvette.D. White enamel, Roman chapters, outer minute ring, subsidiary sunk seconds, snap-on fit. Blued steel ?spade? hands. M. 42.8 mm (19'''), gilded bar calibre, gold train, unusual escapement which combines chronometer and lever with constant force action: the escape wheel consisting of two wheels, the lower delivering the impulse, the upper for locking. The impulse is delivered to a roller mounted inewels on a pivoted detent. The roller turns freely to minimalize the friction, the locking spring is part of the detent mounted perpendicularly to it. On the detent there is a spiral spring that acts as a remontoir power. The end of the detent is fitted with a large roller mounted in jewels which 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 off the half-cylinder. The constant force springs mounted on an adjustable plate to control the energy 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.