- Museum number
SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT.
Full-plate; fusee; Harrison's maintaining power.
Arnold spring detent escapement; Earnshaw type balance.
Later white enamel dial.
Later silver case hallmarked 1816.Casemaker's mark J.D
- Production date
Diameter: 53 millimetres (case)
Diameter: 46.20 millimetres (dial)
Thickness: 21.70 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. 1806. This watch fits into the same series as registration nos 1958,1201.1580-3 and 1958,1201.1842.
Signature: 'Jn° R Arnold London Invt et Fecit No. 1962'.
Case: Later silver case, maker's mark J.D., London hallmark for 1816. Diam. 53 mm, overall h. 21.8 mm.
Dial and hands: Later dial and hands, the enamel dial with the inscription 'Chronometer' and the number 1962 in the upper half.
Dial plate diam. 47.0 mm; front plate diam. 42.3 mm; back plate diam. 41.3 mm; frame h. 8.0 mm.
Frame: Similar to 1958,1201.1580-3. The detent slot has a piece let in and soldered at the foot end and has been further filed to admit a replacement detent.
Fusee: Similar to 1958,1201.1582 and 1958,1201.1842. The setting-up ratchet wheel retained on the squared portion of the barrel arbor by a pin.
Going train: Similar to 1958,1201.1580-2 but with an unusual number of beats per hour caused by the escape wheel of sixteen teeth.
Jewelling: The pivots of the fourth wheel in pierced jewels and those of the escapement in pierced jewels with endstones. A clear sapphire endstone in a blued steel ring on the balance cock.
Escapement: Arnold spring detent escapement probably a good deal altered in detail. The escape wheel has three arms instead of the usual four and sixteen teeth instead of fifteen; the impulse faces have been filed at some time but still show signs of wear. The jewelled discharge roller is as usual but the badly rusted detent is certainly a replacement. The impulse roller also a replacement as the impulse face is leaning towards a radius from the centre to the rounded impulse corner, instead of being on this radius. The impulse face is not jewelled, but both it and the edge, top and bottom of the roller are polished.
Balance: Two-armed brass and steel bimetallic balance of Earnshaw type, the steel parts blued. Segment-shaped brass compensation weights held in by screws from the inside. Timing screws set in the rims at the ends of the arms. Diam. of rim 18.3 mm, h. 1.71 mm.
Balance spring: Blued steel spiral spring with an overcoil and terminal curve, pinned to a blued steel stud on the balance cock.
Balance cock: The upper surfaces engraved with an acanthus leaf and flower motif and with a cornucopia of flowers.
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 80 teeth, 4 arms
Escape pinion 8 leaves, wheel 16 teeth, 4 arms
Beats per hour: 19,200
Cannon pinion 12 leaves, minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Belk in 1932.
- Not on display
Latest: 4 (Nov 2018) Detent (stored separately) very corroded, soaked with oil to keep out moisture. Rest of watch ok.
5 (2017) active rust on detent
5 (Oct 1995) Active rust on detent spring
5 (Jun 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.1840 (Ilbert Collection)
Previous owner/ex-collection number: M214 (Ilbert Ledger)