- Museum number
POCKET-CHRONOMETER MOVEMENT WITH ARNOLD'S SPRING DETENT ESCAPEMENT AND DIAL WITH SUBSIDIARY SECONDS.
Pocket chronometer movement and dial.
Full-plate; fusee; Harrison's maintaining power;
Arnold spring detent escapement; Arnold OZ balance; Helical gold balance spring.
White enamel dial, hours I-XII, subsidiary seconds; numbered 358.
- Production date
Diameter: 41.10 millimetres (back-plate)
Diameter: 43.70 millimetres (dial)
Thickness: 19.40 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by John Arnold and Son, 1787-1799 (No 327/628 has the hallmark for 1786)
Signature: 'John Arnold & Son London Inv.t et Fec.t No 358/659'.
Dial and hands: The dial secured directly to the front plate of the movement by three feet and pins. The front plate turned to resemble a dial plate, and recessed to protect the edge of the dial. The dial numbered 358. On the backfired in red very faint N 358. Red gold 'beetle and poker' hands, and gold seconds hand.
Similar to registration nos. 1958,1201.1576-7. Front plate diam. 43.7 mm; back plate diam. 40.4 mm; frame h. 10.4 mm.
Frame: Similar to 1958,1201.1576-7.
Fusee: Similar to 1958,1201.1576-7.
Going train: Similar to 1958,1201.1576-7.
Jewelling: Similar to 1958,1201.1576-7. The impulse roller not jewelled, but the impulse face polished.
Escapement: Similar to 1958,1201.1576-7. The detent a later replacement, with a rectangular foot, and the empty steady pin hole of the original detent still visible. The escape wheel teeth are marked on the impulse surfaces in two distinct places, indicating that the adjustment of the escapement was different with the replacement detent.
Balance: 'oz' balance similar to 1958,1201.1576 with the addition of two steel screws set radially in the compensating rims near the compensation screws, to aid in poising, also the outer metal in the rims is a silver brass. One of the compensation screws has a ring turned in it, presumably also for poising. A small gold pin is set standing up from the rim near one compensating screw as in 1958,1201.1576. Diam. 25.0 mm, h. 2.3 mm.
Balance spring: Gold helical spring of 5 turns now distorted, with terminal curves, pinned to a blued steel collet and stud on the balance cock, both with square holes.
Going-train counts: As 1958,1201.1576-7.
Motion work: As 1958,1201.1577.
Provenance: Ilbert Collection.
Note: The mainspring although broken is apparently original. H. 4.72 mm, th. 0.22 mm. Inside diam. of barrel 17.4 mm; available h. inside barrel 4.94 mm.
The mainspring is signed, but very indistinctly, the inscription could be 'May 4 14 Arnold'.
- Not on display
Latest: 3 (2017)
3 (Sep 1995) Severely distorted helical spring.
- 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.1578 (Ilbert Collection)
Previous owner/ex-collection number: P103 (Ilbert Ledger)