- Museum number
SILVER CASED POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT AND NO SECONDS INDICATION.
Full-plate; fusee; Harrison's maintaining power.
Arnold spring detent escapement.; Earnshaw type balance.
White enamel dial, hours I-XII, signed.
Later silver case: London.1886, maker's mark PW, pendant London 1885 maker's
mark P.W in cameo.
- Production date
Diameter: 53.70 millimetres (case)
Diameter: 46 millimetres (dial)
Thickness: 19.70 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 Roger Arnold, c. 1820
Signature: 'On the exceptionally large barrel bridge 'John R. Arnold London No 3772'.
Case: Later silver open face, maker's mark P W and with London hallmark for 1886. Pendant has mark PW with London hallmark for 1885. The movement retained by two large dog screws with polished rounded heads on the back plate, these screws added later. Diam. 53.5 mm, overall h. 19.7 mm.
Dial and hands: Flat enamel dial without subsidiary seconds, signed Arnold London in Gothic script across the middle. The back of the enamel dial signed 'Sanders, Arnold London 3772' and '12, Hour'(?) Probably in the same series as registration no. 1958,1201.1844.
Blued steel minute and hour hands, the minute hand not original.
Ebauche marks 220 on the front plate under the dial.
Dial plate diameter 46.4 mm; front plate diam. 43.7 mm; back plate diam. 40.7 mm; frame h. 7.3 mm.
Frame: Full plate with very large detachable barrel bridge, four turned pillars, the back plate retained by pins. Neither hinge nor case catch apparently ever fitted. No dust pipe around the winding square. Dial plate scratched '3 hole Arnold Sanders'.
Fusee: Keywind fusee fitted with stop-work and maintaining power, brass maintaining ratchet wheel, the maintaining detent and return spring of blued steel. The setting-up-work on the front plate under the dial.
Going train: A different count is used to any of the other examples by either Arnold. The layout of the train is quite normal.
Jewelling: The fourth pivot on the dial side only in a pierced jewel. The pivots of the escapement in pierced jewels with endstones, that in the balance cock a plain ruby endstone set in a blued steel ring. The impulse and discharge rollers and the detent jewelled on their acting surfaces.
Escapement: Arnold spring detent escapement, with brass escape wheel with sixteen teeth, their acting surfaces marked. The grey steel detent set with its foot on the edge of the back plate. Detent banking by means of a gold disc screwed eccentrically. The D-shaped locking stone made from a round piece of ruby instead of the usual flat slip, now broken. The passing spring gold, attached by a single rivet.
Balance: Bimetallic balance of Earnshaw type with very narrow crossbar, and brass segment weights clamped by polished rounded steel screws. No graduations on the outer edges of the rims. Timing and poising screws set in the rims at the ends of the crossbar. Diam. of rim 16.5 mm, h. 1.90 mm.
Balance spring: Blued steel flat spiral spring without terminal curve pinned to an overhanging polished steel stud with square hole screwed to the barrel bridge near to the winding square, brass rectangular collet with round hole. A blued steel index fitted under the balance cock and with its tail passing over a graduated sector on the barrel bridge.
Balance cock: Asymmetrical and without decoration.
Great wheel (fusee) 60 teeth
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 70 teeth, 4 arms
Escape pinion 7 leaves, wheel 16 teeth, 4 arms
Beats per hour: 19,200
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 36 teeth, minute wheel 40 teeth
Provenance: Ilbert Collection, purchased by Ilbert from Ash in 1932.
- Not on display
Latest: 3 (2017)
4 (Oct 1995)
- 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.1845 (Ilbert Collection)
Previous owner/ex-collection number: M112 (Ilbert Ledger)