- Museum number
POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT CONVERTED TO DOUBLE-TOOTH DUPLEX.
Spring detent escapement, converted to double-tooth duplex.
One of sugar-tongs missing.
- Production date
- 1800 - 1802
Diameter: 42.50 millimetres
Thickness: 17.70 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Thomas Earnshaw, c. 1800
Signature: On the back plate 'Thos Earnshaw Invt et Fecit No 598'. On the barrel bridge 'London 3041'.
Dial and hands: None.
Front plate diam. 42.75 mm; back plate diam. 41.6 mm; frame h. 7.6 mm.
Frame: The dial plate with the movement hinge is missing, there was no dust cover. Otherwise similar to registration no. 1958,1201.1733.
Fusee: Similar to 1958,1201.1733.
Going train: Similar to 1958,1201.1733.
Jewelling: Only the pivots of the escape pinion and balance arbors in pierced jewels with endstones. The endstone in the balance cock a ruby set in a blued steel ring.
Escapement: Originally an Earnshaw detent escapement was fitted as in registration no. 1958,1201.1592. Later the original detent and brass fixing arm and the brass banking piece were removed, all the holes for these are now empty. At some time a dovetailed detent and brass clamping block were fitted, the brass block being still in place. The escapement is now a Chinese duplex. The steel screw in the edge of the back plate for adjusting the original detent fixing is still in place.
Balance: Plain polished steel three-armed balance. Diam. 25.15 mm, h. 0.51 mm.
Balance spring: Flat spiral steel spring, crudely made and not blued, pinned to a gilded stud screwed to a plate on the back plate, the stud partly obscuring the number of the watch.
Thermal compensation: Remains of sugar tongs, see 1958,1201.1733.
Going-train counts: as originally fitted.
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 15 teeth, 3 arms
Beats per hour: 18,000
The present six-leaf escape pinion and twelve-teeth escape wheel are later substitutes.
Cannon pinion only remaining, 10 leaves.
Provenance: Ilbert Collection, purchased by Ilbert from Goebel in 1931.
- Not on display
Latest: 4 (2017) rust on ratchet wheel and wheel bridge screw
4 (Oct 1995) Fourth wheel and escape wheel pivot broken. Minute wheel missing. Spring detent missing, although foot remains.
- 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.1594 (Ilbert Collection)
Previous owner/ex-collection number: L82 (Ilbert Ledger)