- Museum number
SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement.
Silver case; engine turned; hallmark.
- Production date
- 1837 (case)
Diameter: 56.30 millimetres (case)
Diameter: 50.20 millimetres (dial)
Thickness: 22.80 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by W. B. Clarke, 1837
Signature: 'W. B. Clarke London'.
Case: Open face silver case with the London hallmark for 1837 and the maker's mark C.H. Pendant maker's mark W.O.(?) in a cameo, also hallmark for London 1837 on the pendant. Diam. 56.0 mm, h. 23.0 mm.
Dial and hands: Flat enamel dial of pale yellow-brown colour. Roman hour numerals, subsidiary seconds at 6 o'clock. Brass minute and hour hands, steel seconds hand.
Ebauche marks 22, 12.
Dial plate diam. 50.6 mm; front plate diam. 48.0 mm; back plate diam. 44.6 mm; frame h. 8.0 mm.
Frame: Full plate with four turned pillars, the back plate retained by blued steel screws. Detachable barrel bridge. The dial plate carrying the dial and movement hinge attached to the frame with three short pillars and pins. The case catch and spring mounted on the front plate under the dial. No dust cover. The frame and dial plate gilded. The setting-up ratchet with a spring.
Fusee: Keywind fusee with the usual stop-work and maintaining power, the maintaining ratchet wheel of steel. The polished steel setting-up-work mounted on the barrel bridge. The maintaining detent and return spring of polished steel. The barrel arbor squared at both ends.
Going train: Not unusual except the great wheel has fifty-nine teeth. The brass wheels gilded.
Jewelling: The pivots of the fourth and escapement arbors in pierced jewels, the escapement with endstones. A diamond endstone set in a blued steel ring on the balance cock.
Escapement: Earnshaw style of spring detent escapement, the gilded brass four-armed escape wheel with teeth of Earnshaw pattern, the pivots and those of the balance staff of the form which he used. The impulse roller with radial impulse pallet, the usual jewelled discharge roller. The detent with solid foot mounted on a brass block dovetailed in a slot in the back plate and held with two screws. The single screw to hold the detent also passing down from the back plate. The gold passing spring held with a screw. The brass banking screw for the detent set in a gilded brass block, the foot pinned and screwed well inside the edge of the back plate.
Balance: Bimetallic two-armed balance with brass segment compensation weights held with polished steel plates and screws. Steel timing screws in the rims at the ends of the arms.
Balance spring: Blued steel helical spring of seven complete turns, and with terminal curves, free sprung to a polished steel stud on the balance cock. Brass collet on the balance staff. Diam. of rim 18.2 mm, h. 1.73 mm.
Balance cock: Plain, without decoration.
Great wheel (fusee) 59 teeth
Centre pinion 12 leaves, wheel 80 teeth, no crossings
Third pinion 10 leaves, wheel 75 teeth, 5 arms
Fourth pinion 10 leaves, wheel 80 teeth, 5 arms
Escape pinion 8 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Webster in 1929.
- Not on display
Latest: 2 (2017)
2 (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: A33/1 (Ilbert Ledger)
Previous owner/ex-collection number: CAI.1725 (Ilbert Collection)