- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement.
- Production date
Diameter: 34.40 millimetres (back-plate)
Diameter: 39 millimetres (dial)
Thickness: 9.10 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Webster and Son, Late 19th century
Signature: On the back plate 'WEBSTER & SON Birchin Lane LONDON No. 9572'.
Dial and hands: Flat enamel dial with sunk subsidiary seconds, secured to the front plate by three short feet and pins. Blued steel hands.
Ebauche marks JM, 5021, 10, 0.
Front plate diam. 39.0 mm; back plate diam. 34.5 mm; frame h. 6.5 mm.
Frame: Three-quarter plate construction with three turned pillars, the back plate secured by recessed blued steel screws. The thickness of the front plate has been so reduced, particularly at the centre, that it has started to buckle. The movement was fixed in its case by a hinge screwed to the dial side of the front plate, and by a case catch and spring opposite. All the brass parts gilded.
Fusee: Keywind fusee with the usual stop-work and maintaining power, with steel maintaining ratchet wheel. The setting-up-work fitted in a shallow recess 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.
Going train: Typical layout and construction, the brass wheels gilded, the steel pinions and arbors well finished and polished.
Jewelling: The fourth arbor lower pivot and the escapement pivots in pierced jewels, those of the escapement with endstones. A diamond endstone in a blued steel ring on the balance cock.
Escapement: A development of Earnshaw's spring detent escapement. The brass escape wheel with arms sunk below the level of the rim and teeth. The polished steel impulse roller with a large V-shaped notch and radial impulse surface. The polished steel jewelled discharge roller, without an adjusting flat, sandwiched between the impulse roller and the balance. The detent held by a screw in a slot at the end of the arm of a steel frame with the banking screw set in a second shorter arm (see registration nos. 1958,1201.1599 and 1958,1201.1598). A triangular locking stone and gold passing spring fitted to the detent, the latter held with a screw.
Balance: Bimetallic two-armed balance with four steel screws, the remaining compensation and quarter screws gold. The steel part of the rim has been blued. Diam. of rim 12.5 mm, h. 1.23 mm.
Balance spring: Blued steel spiral spring of 12¾ turns without overcoil or terminal curve, free sprung to a polished steel stud screwed to the back plate, and a round brass collet.
Great wheel (fusee) 72 teeth
Centre pinion 12 leaves, wheel 64 teeth, 5 arms
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 8 leaves, wheel 70 teeth, 5 arms
Escape pinion 7 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 1935.
- Not on display
Latest: 2 (2017)
3 (Oct 1995) Hands bent.
- 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.1754 (Ilbert Collection)
Previous owner/ex-collection number: N290 (Ilbert Ledger)