Important Collectors' Wristwatches, P...

Hong Kong, Jul 10, 2005

LOT 189

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 backcover, gold, engine-turned cuvette.D. White enamel, Romanchapters, outer minute ring, subsidiary sunk seconds, snap-onfit. Blued steel ?spade? hands. M. 42.8 mm (19???), gilded bar calibre,gold train, unusual escapement which combineschronometer and lever with constant force action: the escapewheel consisting of two wheels, the lower delivering theimpulse, the upper for locking. The impulse is delivered to aroller mounted in jewels on a pivoted detent. The roller turnsfreely to minimalize the friction, the locking spring is part of thedetent mounted perpendicularly to it. On the detent there is aspiral spring that acts as a remontoir power. The end of thedetent is fitted with a large roller mounted in jewels which rollson a half-cylinder mounted on the balance staff, the energy inthe constant force spring gives impulse to the balance via theroller when it rolls off the half-cylinder. The constant force springis mounted on an adjustable plate to control the energy to bedelivered to the balance; in fact it is an amplitude adjustment,cut bimetallic compensation balance, flat balance spring, indexregulator with micrometric screw and adjustable key bracket,wolf-tooth winding wheels, winding only in one direction.Stamped ?FS? inside back cover.Diam. 50 mm.