- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH PIVOTED DETENT ESCAPEMENT.
Pivoted detent escapement; with gold escape wheel.
Diameter: 42.50 millimetres (back-plate)
Diameter: 45.20 millimetres (dial)
Thickness: 12.50 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 Swiss, Late 19th century
Dial and hands: Flat enamel dial with sunk subsidiary seconds, secured to the front plate by two feet and eccentric dog screws. Plain Roman hour numerals, Arabic seconds numerals. The back of the dial marked B.F. and an illegible word beginning T or SL, also the number 2144 scratched in the enamel. The hands missing.
Ebauche marks 2144
Front plate diam. 45.1 mm; back plate diam. 42.6 mm; frame h. 7.4 mm.
Frame: Three-quarter plate construction with three turned pillars, the back plate retained by recessed blued steel screws. A separate sub plate on the dial side of the front plate carries the lower bearings of the third, fourth and escapement arbors. The movement was held in its case by a peg and two dog screws in the edge of the front plate. The brass parts electro-gilded a whitish yellow.
Fusee: Keywind fusee fitted with Harrison's maintaining power with a steel ratchet wheel and four-turn Geneva stop-work in a recess on the dial side of the front plate. Setting-up-work also on the dial side of the front plate, the barrel arbor with an extended square on that end only. The barrel with a flange on the cover end. A chain guard is fitted between the barrel and the balance. The great wheel and maintaining ratchet wheel are held on the bottom of the fusee by a steel plate in a recess in the great wheel and three screws passing into a boss left standing on the ratchet wheel and on which the great wheel also pivots. The squares for both winding and hand setting protected by dust-excluding tubes held on with three screws each.
Going train: Conventional layout and construction, the centre arbor hollow for the squared hand-set arbor carrying the cannon pinion. The brass wheels gilded, the steel pinions and arbors well finished and polished.
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, those of the escapement with endstones. The train jewels with curved faces (bombé) against the pivot shoulders.
Escapement: Pivoted detent escapement, the gold escape wheel lightly made and crossed out, the arms sunk below the level of the rim and teeth. The polished steel impulse roller set with a radial jewel, the discharge roller also polished, with one adjusting flat, and jewelled with a straight-sided jewel in a similar slot. The pivoted detent lightly made with the top surfaces bevelled and polished, the half-round locking stone protruding on the lower side of the detent and banking against a screw head set in the subplate. Locking occurs on the second tooth after that which has just given impulse and the detent is planted with its pivoting point well outside a tangent to the locked tooth. The passing spring appears to be made of gold and is secured to the detent arbor boss by a screw. The blued steel return spring is attached to a brass collet above the arbor boss, and to a polished steel arm screwed in a shallow recess in the front plate.
Balance: Bimetallic two-armed balance, the arms of sage-leaf pattern, with gold quarter screws, the remainder brass. Diam. of rim 14.7 mm, h. 1.78 mm.
Balance spring: Blued steel helical spring of 9 turns, with terminal curves, pinned to a rectangular brass collet slit to spring it onto the balance staff, and a small brass stud held under a steel plate on the balance cock.
Great wheel (fusee) 76 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, 4 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; Ilbert purchased the piece from Malcolm Gardner in 1932.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Hour, minute and seconds hands 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.1826 (Ilbert Collection)
Previous owner/ex-collection number: M93 (Ilbert Ledger)