63,250 HKD
Chas. Smith Nr 122 Bunhill Row, London, No. 833, circa 1785. Very rare silver cased pocket chronometer with regulator dial in the manner of Charles Haley. Purpose built Iater three body with engine-turned band and spun back (London hallmark 1835). Full plate gilt with turned pillars, fusee with chain, Arnold spring detent escapement, the detent inset into the plate, bi-metallic two arm Z balance (blued-steel and silver with threaded counterpoise screws on the ends, helical blued-steel spring free sprung with terminal curves engraved balance cock with large diamond end stone. Signed on the movement. In very good condition. Diam. 54 mm. Notes This watch incorporates an apparently unrecorded device to reduce the arc of the balance when necessary to prevent overbanking. An additional roller stepped on the upper part and horizontally grooved on the circular section is fitted below the standard steel impulse roller. The vertical section of the potance supporting the balance staff is slotted with a protruding section of gold tube flattened at the outer end. It may be that light feather springs, much in the style of the gold passing spring for the detent were wedged within the tube and brought into contact with the extra roller if the arc of the balance exceeded the intended amount, acting as a form of brake. The parts that would have made contact between the roller and the tube are now lacking If the system worked something in the manner as described above, it would have the a Read more…
Auctioneer:
Antiquorum
Date:
1992-05-24
