- Museum number
POCKET-CHRONOMETER MOVEMENT WITH [?] COUP PERDU ESCAPEMENT.
Lever escapement with bar movement.
Gt wheel 80
Centre wheel 64/10
4th wheel 60/8
Escape wheel 16/6
Canon pinion 10
Minute wheel 30
Minute pinion 8
Hour wheel 32
Diameter: 45.70 millimetres (dial)
Diameter: 45.50 millimetres
Thickness: 7.70 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Maker unknown (Swiss or French)
Dial and hands: Enamel dial with curved edge. Hands missing.
Ebauche marks 89 and underneath 653.
Front plate diam. 44.7 mm, frame h. 4.2 mm
Frame: Lepine-type calibre with hanging barrel, and with separate cocks on both sides of the front plate to make the movement as thin as possible. Brass parts gilded (see Note).
Going barrel: The usual construction, key wind with four-turn Geneva stop-work on the cover end.
Going train: The usual construction. The wheels not gilded.
Escapement: Pivoted detented escapement specially adapted for a thin calibre. The detent is returned by a leaf spring and the locking stone protrudes sideways from the body of the detent. Steel impulse roller with radial impulse plane, jewelled discharge roller.
Balance: Plain brass three-armed balance, the flat spring with an index on the balance cock. No compensation. Diam. 18.1 mm, h. 0.48 mm.
Balance spring: Blued steel spiral spring of 10 turns, no terminal curves.
Great wheel (barrel) 80 teeth
Centre pinion 10 leaves, wheel 64 teeth, 5 arms
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 60 teeth, 4 arms
Escape pinion 6 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Cannon pinion 10 leaves, minute pinion 8 leaves
Hour wheel 32 teeth, minute wheel 30 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1936.
Note: Although not made for the greatest accuracy, this movement is an example of the use of a precision escapement in a very thin movement, presumably in the hope of a better performance than would be obtained with a cylinder or duplex escapement. The calibre was probably one originally fitted with a cylinder escapement. It retains the adjustable chariot to move the balance assembly towards or away from the escape wheel, and the parts used to convert it are of a different standard and finish from the movement. The main plate has a split (no doubt caused whilst being worked upon) from the slot clearing the pallets to the outside edge.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Hour, minute and seconds hands missing.
- 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.1611 (Ilbert Collection)
Previous owner/ex-collection number: P99 (Ilbert Ledger)