- Museum number
EBAUCHE OF SUBSIDIARY SECONDS POCKET-CHRONOMETER BAR MOVEMENT WITH PIVOTED DETENT ESCAPEMENT [UNFINISHED, UNDIALLED].
Pivoted detent escapement; unfinished ebauche.
Diameter: 43 millimetres
Thickness: 13.70 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Maker Unknown, but Swiss, Late 19th century
Dial and hands: None.
Ebauche marks 12,169.
Front plate diam. 42.9 mm; frame h. 5.5 mm; front plate th. 3.0 to 3.05 mm (sunk out to 1.55 to 1.60 mm).
Frame: Bar movement built up on the front plate, recessed under the dial and with a semicircular bridge for the third, fourth and escapement lower bearings. No provision for a dial or for holding the movement in a case.
Going barrel: Hanging barrel with four-turn Geneva stop-work. The barrel arbor drilled for a retaining pin for the stop-work finger. The cover positioned by a pin half in the barrel wall which fits into a matching slot in the cover.
Going train: The pinions, arbors and pivots polished, the brass wheels left rough and awaiting finishing and gilding. The centre pinion drilled for the hand-set arbor.
Jewelling: Only the pivots of the escapement in jewelled holes, with endstones set in plates.
Escapement: Pivoted detent, the brass escape wheel with the crossings sunk below the level of the rim and teeth. The pivoted detent with poising tail and top surfaces bevelled and polished. Jewel locking stone serving also for banking in a hole in the front plate. Spiral return spring of 7½ tight coils pinned to a brass collet and polished steel stud. Gold passing spring screwed to the detent boss. The impulse roller with polished edge and crescent, and with a radial impulse pallet. The discharge roller made from a solid piece of ruby and held with a brass cap on the end of the balance staff. The detent planted outside a tangent to the locked wheel tooth, this tooth being the second after that which has just given impulse.
Balance: Bimetallic two-armed balance, the arms meeting the rim about half way up. The compensation screws probably a low carat gold alloy. Diam. 17.2 mm, h. 1.39 mm.
Balance spring: Blued steel open coiled spiral spring of 11½ turns, with an overcoil and terminal curve with reversed curve. An index fitted on the balance cock.
Great wheel (barrel) 76 teeth
Centre pinion 10 leaves, wheel 80 teeth, 5 arms
Third pinion 10 leaves, wheel 75 teeth, 5 arms
Fourth pinion 10 leaves, wheel 70 teeth, 5 arms
Escape pinion 7 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Motion work: Missing.
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1931.
- Not on display
Latest: 3 (2017)
4 (Oct 1995)
- Acquisition date
- Acquisition notes
- Following the successful acquisition of the celebrated Ilbert collection of clocks (1958,1006 collection), prints and other related materials made possible by the generous donation of funds by Gilbert Edgar CBE Ilbert's watches were then acquired using funds provided by Gilbert Edgar, public donations and government funds.
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.2388 (Ilbert Collection)
Previous owner/ex-collection number: L113 (Ilbert Ledger)