- Museum number
SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement; 3 arm compensated balance.
- Production date
Diameter: 55.70 millimetres (case)
Diameter: 48.10 millimetres (dial)
Thickness: 24.40 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Ellicott, 1820
Signature: On the back plate 'ELLICOTT Royal Exchange London 9920'; the signature repeated on the dial below the figure XII.
Case: Open face silver case with the London hallmark for 1820 and the maker's mark W.R. The glazed bezel and back hinged to the middle with gold joints, the fixed dome with hole for winding. No case springs. A dumpy pendant and heavy ring bow. The back worn through. Diam. 55.7 mm, h. over glass 24.2 mm.
Dial and hands: Flat enamel dial, slightly cracked, with subsidiary seconds, signed in the upper half.
Gold minute and hour hands, steel seconds hand with a gold boss.
Ebauche marks C & N, 13°.
Dial plate diam. 49.1 mm; front plate diam. 47.3 mm; back plate diam. 44.0 mm; frame h. 8.4 mm.
Frame: Similar to registration no. 1958,1201.1596, but without a dust ring or cover.
Fusee: Similar to 1958,1201.1596, note the return spring for the setting-up-pawl in place on the barrel bridge, and also the turned oil retention rings around the third and fusee arbor bearings on the backplate, the other plain bearings similarly turned.
Going train: Similar to 1958,1201.1596.
Jewelling: Both fourth arbor pivots run in pierced jewels. The pivots of the escape pinion arbor and balance staff run in pierced jewels with endstones. Diamond endstone set in a blued steel ring on the balance cock.
Escapement: Earnshaw type of detent escapement with gilded brass escape wheel, sunk out on the upper side to leave only the teeth standing proud of the rim. The teeth occupying about half a pitch, with backs slightly rounded. The thick steel impulse roller polished all over and with radial impulse jewel. The jewelled polished discharge roller without a flat for adjustment.
The very well-made detent held by a single screw in a slot in the back plate. The passing spring of steel pinned to a block (cf. Thomas Earnshaw registration no. 1958,1201.1592), half-round ruby locking stone of 0.45 mm diam. The detent planted with the foot well inside a tangent to the tip circle of the escape wheel at the locked tooth. The detent horn is therefore bent towards the passing spring which is thus held well clear of the detent.
Balance: Bimetallic three-armed balance, the brass segment weights held by steel plates and screws.
Balance spring: Blued steel helical spring of 5½ turns, and with terminal curves, free sprung to a polished steel stud on the balance cock. A brass collet on the balance staff. Diam. of rim 19.2 mm, h. 2.2 mm.
Great wheel (fusee) 60 teeth, worn
Centre pinion 12 leaves, wheel 80 teeth, no crossings
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 12 leaves, minute pinion 16 leaves
Hour wheel 48 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection, purchased by Ilbert from Malcolm Gardner in 1933.
- Not on display
Latest: 4 (2017) bit of rust on balance
4 (Oct 1995)
Most of third wheel arbor missing.
- 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.2091 (Ilbert Collection)
Previous owner/ex-collection number: M169 (Ilbert Ledger)