- Museum number
SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT.
Full-plate; fusee; Harrison's maintaining power.
Arnold spring detent escapement. Later Pennington type balance.
White enamel dial, hours I-XII, subsidiary seconds 10-60.
Gold hour and minute hands, blued-steel seconds hand, all probably replacements.
Later silver case.
- Production date
Diameter: 58.70 millimetres (case)
Diameter: 51.60 millimetres (dial)
Thickness: 27.80 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
Signature: Engraved on the back plate 'John Arnold and Son London Invt. et Fect No 125'.
Case: Later plain silver case with London hallmark for 1790, 1810 or 1830 but probably 1830 and maker's mark GR. Bezels front and back snapping shut on the middle. The movement hinged to the case at 12 o'clock and with a catch opposite. Diam. 58.8 mm, overall h. 26.6 mm.
Dial and hands: Flat enamel dial with short feet pinned directly to the front plate of the movement, no dial plate. The dial signed ARNOLD & SON LONDON and numbered 225.
Pale yellow gold minute and hour hands, blued steel seconds hand, probably all replacements.
No dial plate. Front plate diam. 51.0 mm; back plate diam. 48.1 mm; frame h. 11.9 mm.
Frame: Full plate (gilded brass) with four turned pillars, the back plate retained by pins. The bearings for the pivots of the going train are now brass bushes let into the plates and retained by blued steel screws but were probably originally in jewels. The movement hinge riveted directly to the front plate under the dial. The case catch held by a shoulder screw on the inside of the front plate, its return spring a later replacement passing over the holes for the original maintaining detent spring.
Fusee: Keywound and provided with the usual stop-work and maintaining power, the maintaining ratchet wheel brass. Blued steel maintaining detent pivoted in the frame well in from the edge, with a return spring set in a screw in the top plate, a later replacement of a spring originally screwed to the inside of the front plate. The stop piece return spring fixed to the stop piece itself.
Going train: Going-train wheels gilded brass, pinions well finished and polished.
Jewelling: Only the escapement pivots now run in pierced jewels with endstones. The escapement having a jewelled locking stone on the detent and a normal jewelled discharge pallet, but the impulse roller made from a solid piece of clear sapphire.
Escapement: Arnold spring detent escapement with brass escape wheel, the locking corners of the teeth damaged. The detent probably not original; the top of the foot polished, the rest left grey. Gold passing spring riveted on. The detent banking against a screw set in the back plate.
Barrel: Large barrel with flange at the top plate end. The setting-up-work mounted under the dial plate.
Balance: Later Pennington-type replacement. The bimetallic rims made separately from the crossbar of brass, and secured to this by screws. Steel quarter and compensation screws with special split collar friction device. Diam. of rim 20.5 mm, h. 2.75 mm.
Balance spring: Later helical balance spring, the upper end secured to a brass stud on the balance cock, long rectangular brass collet.
Balance cock: Finely pierced and engraved decoration of gryphons and acanthus leaves. At some time the cock has been broken between the gryphon and the end with the stud and balance upper bearing; the repair crudely executed with soft solder.
Great wheel (fusee) 60
Centre pinion 12 leaves, wheel 75 teeth, no crossings
Third pinion 10 leaves, wheel 64 teeth, 4 arms
Fourth pinion 8 leaves, wheel 80 teeth, 4 arms
Escape pinion 8 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, hour wheel 42 leaves
Minute pinion 14 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1936.
- Not on display
- Latest: 3 (2017)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.1841 (Ilbert Collection)
Previous owner/ex-collection number: P33 (Ilbert Ledger)