- Museum number
POCKET CHRONOMETER MOVEMENT AND DIAL WITH THIRTY-HOUR UP-AND-DOWN DIAL AND SUBSIDIARY SECONDS.
1/2-plate movement; fusee; Harrison's maintaining power; Keyless winding.
Earnshaw spring detent escapement; split bimetallic balance; helical balance spring.
White enamel dial, Roman hours I-XII, sunk subsidiary seconds, Up-and-down dial; signed and numbered.
Blued-steel hands. Chalfont's keyless mechanism.
- Production date
Diameter: 39.60 millimetres (back-plate)
Diameter: 43.30 millimetres (dial)
Thickness: 10.40 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by John Bennett, c. 1870
Signature: 'Jno. Bennett 65 and 64 Cheapside LONDON NO 15425.'
On the dial 'JOHN BENNETT 65 AND 64 CHEAPSIDE LONDON 15425'.
Dial and hands: Enamel dial, on the back 25. Blued steel hands.
Ebauche marks 14 x 1, E.S. 25.
Front plate diam. 43.3 mm; back plate diam. 40.0 mm; frame h. 7.8 mm.
Frame: Half plate hunter calibre, with Chalfont fusee keyless work.(1) The frame built up on a thick front plate having three turned pillars and the back plate secured by screws. The front plate recessed under the dial to accommodate the fusee keyless work, the motion work, the setting-up-work, the up-and-down work and a detachable plate carrying the third, fourth and escapement lower bearings. The dial fixed directly to the front plate by three feet and pins. The movement retained in its case by a positioning peg and single dog screw.
Fusee: Fitted with the usual stop-work, and maintaining power with steel ratchet wheel and click pivoted between the plates. The stop-work spring and stop-piece made of a single piece of blued steel. The setting-up-work under the dial. The pivots of the fusee in detachable brass bushes.
Going train: The centre pinion hollowed out for the handset arbor carrying the pinion.
Jewelling: The third, fourth and escapement pivots running in pierced jewels, those of the escapement with endstones. Diamond endstone set in blued steel ring on the balance cock.
Escapement: Earnshaw type of detent escapement. The three-armed escape wheel of brass, the polished steel impulse roller jewelled so that the impulse plane is on a radial from the centre. The usual jewelled discharge roller mounted below the impulse roller. The polished steel detent is fitted with a half-round locking stone and the gold passing spring is held by a screw. The steel banking piece for the detent is concentric with the balance staff and carries a gold banking screw.
Balance: Bimetallic two-armed balance with gold compensation and quarter screws, straight crossbar. Diam. of rim 15.7 mm, h. 1.94 mm.
Balance spring: Blued steel helical spring of 6 turns, with terminal curves, free sprung to a steel stud on the balance cock. Brass rectangular collet on the balance staff.
Great wheel (fusee) 84 teeth
Centre pinion 12 leaves, wheel 80 teeth, 6 arms
Third pinion 10 leaves, wheel 75 teeth, 6 arms
Fourth pinion 10 leaves, wheel 80 teeth, 6 arms
Escape pinion 8 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 10 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, steel minute wheel 30 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1940.
(1) Chalfont fusee keyless work is illustrated and described in David Glasgow, 'Watch and Clockmaking', London, 1885, pp. 272-4.
- Not on display
Latest: 3 (2017)
3 (Mar 1996)
- 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.1588 (Ilbert Collection)
Previous owner/ex-collection number: Q185 (Ilbert Ledger)