- Museum number
SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH PIVOTED DETENT ESCAPEMENT, FORMERLY WITH DUST-CAP.
Pivoted detent escapement.
- Production date
Diameter: 53.50 millimetres (case)
Diameter: 44.50 millimetres (dial)
Thickness: 20.40 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by George Edwarts, 1903
Signature: On the barrel bridge 'George Edwarts 005'. On the back plate 'CHRONOMETER MAKER TO THE ADMIRALTY LONDON'.
Case: Open face silver case with the Chester hallmark for 1903 and the maker's mark J.M.K. surmounting a I. The inner dome numbered 005. The middle with fine reeding, the back engine-turned with an oval central cartouche and opening with a single fly spring, and a case catch and spring operated by a push-piece in the pendant. The pendant hallmarked and with the maker's mark CH. Diam. 53.5 mm, overall h. 20.4 mm.
Dial and hands: Flat enamel dial with sunk central portion and subsidiary seconds, and inscribed CHRONOMETER in the upper half of the centre, secured directly to the front plate by three feet and pins. On the back of the dial in the enamel 86. Blued steel hands, all replacements.
Ebauche marks 18 4 W.B., and 005, 005 also on the train bridge.
Front plate diam. 46-6 mm; back plate diam. 41.2 mm; frame h. 8.2 mm.
Frame: Full plate construction with four turned pillars,(1) the back plate retained by two blued steel screws and two pins. A detachable barrel bridge, no dial plate but the front plate recessed for all the under dial work. The movement hinge and case catch fitted on the front plate under the dial. There was once a dust cap, now missing. All the brass parts gilded, probably electro-gilded after acid etching.
Fusee: Key wind fusee with the usual stop-work and maintaining power, the maintaining ratchet wheel steel. The setting-up-work fitted on the dial side of the front plate, in a shallow recess. The barrel arbor with an extended square on that end only.
Going train: The usual layout and construction, the brass wheels burnished, the steel pinions and arbors well finished and polished.
Jewelling: The pivots of the fourth and escape pinion arbors in pierced jewels, those of the balance staff in pierced jewels with endstones.
Escapement: A form of pivoted detent escapement. The brass escape wheel left the full thickness, and locked by a triangular, clear sapphire, locking stone. The steel detent pivoted in the frame, the pivoting point planted well inside a tangent to the locked tooth. A blued steel spiral return spring acts by the free outer end resting against the detent. The passing spring also of blued steel pinned into a block set in the short detent tail. Banking provided by a strong brass pin in the path of the detent tail. The impulse roller with polished edge and notch, the impulse face leaning slightly towards a radius to the tip. Grained steel discharge roller with a jewel.
Balance: Bimetallic two-armed balance with brass screws. Diam. of rim 17.4 mm, h. 1.62 mm.
Balance spring: Blued steel spiral spring of 10½ turns, without an overcoil or terminal curve, pinned to a polished steel stud on the balance cock. 5 scratched on the underside of the cock. A polished steel index fitted on a boss concentric with the balance upper bearing.
Great wheel (fusee) 75 teeth
Centre pinion 10 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 10 leaves, wheel 75 teeth, 5 crossings
Escape pinion 10 leaves, wheel 16 teeth, 4 crossings
Beats per hour: 14,400
Cannon pinion 14 leaves, brass minute pinion 12 leaves
Hour wheel 48 teeth, minute wheel 42 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1932.
(1) This is exceptionally late for a full plate movement; it is possibly re-cased.
- Not on display
Latest: 2 (2017)
3 (Oct 1995) Dust-cap 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.1734 (Ilbert Collection)
Previous owner/ex-collection number: M296 (Ilbert Ledger)