- Museum number
GOLD CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Full-plate; fusee; Harrison's maintaining power.
Earnshaw type spring-detent escapement; Earnshaw-type compensation balance.
White enamel dial, hours I-XII, subsidiary seconds 10-60, signed and numbered.
Gold hour and minute hands, replacement blued-steel seconds hand.
Later gold case with hallmark and casemaker's mark.
In the middle of the case back an engraved crest, 'an eagle displayed'.
- Production date
Diameter: 55.80 millimetres (case)
Diameter: 47.20 millimetres (dial)
Thickness: 20.60 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Barwise and Sons, c. 1820
Signature: 'Barwise and Son's London No 7350'.
Case: Later 18-carat gold consular case (probably recased by Barwise) with the London hallmark for 1837 and the maker's mark, W.W., surmounted by an axe, in the inner case, numbered inside the dome 7350. The back and bezel engine-turned. A small crest of a displayed eagle on a wreath in the centre of the back. Diam. 55.6 mm, h. 20.4 mm.
Dial and hands: Flat enamel dial with subsidiary seconds at 6 o'clock, signed 'Barwise's No 7350' in the upper half. Gold minute and hour hands, blued steel seconds hand.
Ebauche marks ---8.
Dial plate diam. 48.0 mm; front plate diam. 46.3 mm; back plate diam. 43.8 mm; frame h. 7.3 mm.
Frame: Full plate with four turned pillars, the back plate secured by pins. Detachable barrel bridge. The dial plate carrying the case hinge, the catch and spring under the dial on the front plate. The movement originally fixed in the case with a pin and two screws through the case edge. No dust cover. Both plates numbered 7350 on their inner surfaces.
Fusee: Key wind fusee, with stop-work and maintaining power, the maintaining ratchet wheel brass. Setting-up-work on the front plate under the dial, the barrel arbor squared at both ends.
Going train: The brass wheels gilded.
Jewelling: The fourth lower and escapement pivots in pierced jewels, those of the escapement with endstones. A diamond endstone in a blued steel ring on the balance cock.
Escapement: Earnshaw type of detent escapement with ungilded brass escape wheel of Earnshaw style. Steel impulse roller, not jewelled, the bottom surface polished. The radial impulse plane not polished.
The dovetailed detent with half-round locking 'stone' of steel, set in a brass block carrying the banking screw, apparently all later replacements. Originally a detent was fitted with its foot screwed to the underside of the back plate. The holes for the detent remain, and also a brass banking piece, no longer used.
Balance: Bimetallic balance of Earnshaw type with segment brass compensation weights secured by radial screws on the inside. Steel timing screws set in the rims at the ends of the crossbar. Diam. of rim 18.0 mm, h. 1.52 mm.
Balance spring: Blued steel spiral spring pinned to a polished steel stud on the back plate near the maintaining detent pivot hole, the brass collet rectangular with rounded ends.
Balance cock: Plain and without decoration. On the centre line of the overhanging portion balance cock is set a brass plug with a screw head, and carrying two pins, one on each side of the last turn of the balance spring. These pins can be turned so as to alter their effective separation and thus provide a facility for isochronal adjustment.
Great wheel (fusee) 60 teeth
Centre pinion 10 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 6 arms
Third pinion 8 leaves, wheel 60 teeth, 6 arms
Fourth pinion 8 leaves, wheel 70 teeth, 6 arms
Escape pinion 7 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, brass minute pinion 15 leaves
Hour wheel 45 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection, purchased by Ilbert from Ash in 1932.
Note: Baillie 1951 gives Barwise and Sons, London, 1819-23.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Escape wheel arbor broken.
- 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.1846 (Ilbert Collection)
Previous owner/ex-collection number: M113 (Ilbert Ledger)