- Museum number
POCKET-CHRONOMETER MOVEMENT WITH PIVOTED DETENT ESCAPEMENT AND REVERSED FUSEE.
Pivoted detent escapement.
Diameter: 40.80 millimetres (back-plate)
Diameter: 43.80 millimetres (dial)
Thickness: 11.40 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 probably Swiss, Late 19th century
Signature: On the back plate 'Charles Nephew & Co LONDON & CALCUTTA'; also on the dial and the number 57 over 1999.
Dial and hands: Flat enamel dial with Roman numerals with sunk subsidiary seconds, attached to the front plate by two feet and pins. The name and number painted in very small characters in the upper half of the dial.
The spade hands and the seconds hand of the characteristic Swiss purple/blue colour.
Ebauche marks B 877.
Front plate diam. 43.9 mm; back plate diam. 41.0 mm; frame h. 7.1 mm.
Frame: Continental three-quarter plate construction with three turned pillars, the back plate retained by recessed steel screws of a purple/blue colour. The movement hinge, case catch and spring attached to the front plate under the dial. All the brass parts gilded. The balance cock engraved with scrolling foliage.
Fusee: Keywind reversed fusee with Harrison maintaining power, steel maintaining ratchet wheel, polished steel main¬taining detent, the return spring screwed and steady pinned to the inside of the front plate concentric with the great wheel. Geneva stop-work mounted on the bridge bearing for the fusee arbor pivot on the front plate under the dial. The barrel arbor with an extended square on the dial side of the front plate carries the polished steel setting-up-work.
Going train: The centre arbor hollow for the squared hand-set arbor which carries the cannon pinion. The steel pinions and arbors well made and polished, the brass wheels gilded.
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, those of the escapement with endstones. The train jewels bombé, and of a bright red colour on the back plate. The polished steel endstone plates on the front plate side of figure-of-eight shape. The balance cock endstone in a type of coquerette of polished steel. The last three features point to a Swiss origin as does the colour of the hands and screws.
Escapement: Pivoted detent escapement, the escape wheel locked on the second tooth after that which has just given impulse. The rim and teeth of the gilded brass escape wheel left standing proud of the deeply sunk arms. Polished steel impulse roller with radially set jewel, and discharge roller with two flats for adjusting, the jewel set in a straight-sided slot. The steel detent with half-round locking stone, held by a steel half-round wedge projecting from the underside and banking against an adjustable plug on the edge of a hole in the escapement bridge. The long return spring acting on a comma-shaped brass piece on the detent staff, and planted between the balance cock foot and the edge of the front plate. The steady pin for this spring is lodged in a slot in the edge of a brass plug set in the front plate, and provided with a screwdriver slot, like that for the detent banking, for adjustment of the spring tension. Later, crudely made, white metal passing spring attached by a screw to the detent boss.
Balance: Double-sunk two-armed bimetallic balance with gold timing nuts at the ends of the arms, and compensation screws. Diam. 16.2 mm, h. 1.26 mm.
Balance spring: Blued steel helical spring of 10 turns, with terminal curves, free sprung to a polished steel stud on the balance cock, and a counterpoised, slotted bass collet.
Great wheel (fusee) 80 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, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, minute wheel 36 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1932.
- Not on display
Latest: 3 (2017)
3 (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.1610 (Ilbert Collection)
Previous owner/ex-collection number: M295 (Ilbert Ledger)