- Museum number
POCKET-CHRONOMETER MOVEMENT WITH ARNOLD'S SPRING DETENT ESCAPEMENT.
Pocket chronometer movement and dial.
Full-plate; separate barrel bridge; fusee; Harrison's maintaining power.
Arnold spring detent escapement; Arnold Z balance; helical blued-steel spring.
White enamel dial, hours I-XII, subsidiary seconds; signed and numbered.
- Production date
Diameter: 43.90 millimetres (back-plate)
Diameter: 49.10 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 John Roger Arnold, c. 1806 (no. 2029 has the hallmark for 1807)
Signature: 'Jn° R. Arnold London Invt. et Fecit no 2014'.
Dial and hands: Perfect enamel dial with cursive signature and number. Fixed as registration no. 1958,1201.1581.
Gold hands, the seconds hand screwed to its pipe.
Dial plate diam. 49.0 mm; front plate diam. 45.0 mm; back plate diam. 44.0 mm; frame h. 8.3 mm.
Frame: Similar but slightly larger than 1958,1201.1581except that the foot of the dust guard round the fusee winding square is a different shape.
Fusee: Similar to registration no. 1958,1201.1582 except that the foot of the setting-up click spring is placed nearer the inner edge of the barrel bridge, and the click itself has a limiting pin set in the barrel bridge.
Going train: Similar to 1958,1201.1581 but the centre wheel and third pinion counts different.
Jewelling: Similar to 1958,1201.1581 except that the endstone plate on the balance cock for the diamond endstone is not blued.
Escapement: Similar to 1958,1201.1581, the impulse faces of the escape wheel teeth marked. The steel passing spring attached to the detent by a single rivet.
Balance: Similar to 1958,1201.1582. Diam. 20.3 mm, h. 2.6 mm.
Balance spring: Blued steel helical spring of 5 complete turns, with a terminal curve at each end. Pinned with square-section steel pins to stud and collet. The stud is not mounted on the balance cock, but is screwed to the back plate at the end of the barrel bridge. It is adjustable by the two round-headed screws where it overhangs the balance, and is made of gilded brass.
Balance cock: Similar decoration to registration nos 1958,1201.1580-2.
Great wheel (fusee) 60 teeth
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, minute pinion 16 leaves
Hour wheel 48 teeth, minute wheel 48 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Jauncey in 1935.
- Not on display
Latest: 3 (2017)
3 (Sep 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.1583 (Ilbert Collection)
Previous owner/ex-collection number: N276 (Ilbert Ledger)