- Museum number
POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement.
- Production date
- 1871 -1873
Diameter: 37.70 millimetres (back-plate)
Diameter: 42 millimetres (dial)
Thickness: 10.20 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Frodsham and Son, c. 1875
Signed: On the back plate 'Frodsham and Son, Gracechurch St., LONDON 6950'. On the dial FRODSHAM, LONDON'.
Case: No case, but was open face.
Dial and hands: Enamel dial with sunk subsidiary seconds, fixed directly to the front plate by three feet and pins, two feet missing.
Blued steel hands, seconds hand missing.
Ebauche marks T + S 14 x 2.
Front plate diam. 42.5 mm; back plate diam. 38.0 mm; frame h. 6.3 mm.
Frame: Three-quarter plate with four turned pillars, the back plate retained by blued steel screws. Movement hinge, case catch and spring mounted on the dial side of the front plate. A large separate bridge on the front plate for the third, fourth and escapement bearings. All the brass parts gilded.
Fusee: Reversed fusee with stop-work and maintaining power, the maintaining ratchet steel. The setting-up-work on the back plate, the barrel arbor squared both ends.
Going train: Arranged in an anticlockwise direction when seen from the back. Well made and finished, the brass wheels gilded.
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, those of the escapement with endstones, a diamond in the balance cock.
Escapement: A development of the Earnshaw detent escapement. The brass escape wheel with arms and rim sunk below the level of the teeth on the upper side. The polished steel banking piece mounted beside the detent and carrying a brass banking screw, providing banking for the detent against the head. The polished steel impulse roller not jewelled, the impulse face radial opposite a hole drilled for poising. The usual jewelled discharge roller with a flat for adjusting. Finely made detent with polished foot, gold passing spring held by a screw, and half-round locking stone, planted with the foot inside a tangent to the locked escape wheel tooth.
Balance: Bimetallic two-armed balance, the steel part of the rims blued, the screws gold. Diam. 17.5 mm, h. 1.38 mm.
Balance spring: Blued steel helical spring of about 5¾ turns, with terminal curves. Brass collet, polished steel stud.
Balance cock: As unusual one: in place of a normal cock on the front plate a brass piece is screwed, presumably for aesthetic purposes; a tapped hole just in front of it is left unfilled.
Going train counts:
Great wheel (fusee) 72 teeth
Centre pinion 12 leaves, wheel 80 teeth, 5 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 12 leaves, minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1933.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Seconds hand 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.1600 (Ilbert Collection)
Previous owner/ex-collection number: M335 (Ilbert Ledger)