- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement; brass balance screwed on bimetallics.
- Production date
Diameter: 41.40 millimetres (back-plate)
Diameter: 50.30 millimetres (dial)
Thickness: 10.90 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by William Pickman, c. 1810
Signature: On the barrel bridge: 'Wm PICKMAN LONDON 3165.'(1)
Dial and hands: Flat enamel dial, scribed rings for the minute and second circles with divisions marked under the enamel. The dial attached to the dial plate by three feet and pins. Only the gold hour hand remaining.
Dial plate diam. 50.3 mm; front plate diam. 48.0 mm; back plate diam. 47.3 mm; frame h. 8.1 mm.
Frame: Full plate construction with detachable barrel bridge, four turned pillars, the back plate retained by pins. The dial plate, carrying the movement hinge and stamped GH, secured to the front plate by four short feet and pins, and with the punched letters G.H. on the underside. The case catch and spring on the front plate under the dial. All the brass parts gilded. The shape of the foot of the winding arbor dust guard and the balance cock should be compared with those of Robert Pennington, registration no. 1958,1201.1743. The balance potence has a straight moulded edge to the foot.
Fusee: Key wind fusee with the usual stop-work and maintaining power, brass maintaining ratchet wheel. Polished steel setting-up-work on the front plate under the dial, the barrel arbor with an extended square at both ends. The barrel with a flange at the cover end and a slight waist to clear the great wheel teeth.
Going train: Well made and finished, the brass wheels gilded, the pinions and arbors polished. The wheel counts do not correspond with either watch by Pennington (registration nos 1958,1201.1738 and 1958,1201.1743).
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, all with screwed-in settings, those of the escapement with endstones. A diamond endstone set in a blued steel ring on the balance cock.
Escapement: A development of Earnshaw's spring detent escapement. The brass escape wheel with small, almost straight-backed teeth, not sunk out, and possibly a later replacement as the collet overlaps the central boss. The impulse roller with edge and bottom polished, and set with an impulse pallet dovetailed in place. The impulse face of this pallet leans slightly away from a radial to its tip. The steel discharge roller also with a dovetailed jewel, and a single flat for adjusting. The detent of the dovetailed type, held by a single screw on the side of a steel block screwed and pinned to the underside of the back plate. Banking for the detent provided against a brass screw in an arm under the escape wheel, and integral with a block screwed and pinned beside the detent block. The foot of the detent very flat, the steel passing spring attached by a screw. The locking stone of large diameter (0.8 mm), with a flat ground on one end for locking, the other end protruding from the detent pipe to provide banking against the screw. The detent planted with its centre line well inside a tangent to the locked tooth.
Balance: Later 'Pennington YCC ' type of balance similar to that of 1958,1201.1743, except that short brass segments are riveted to the inside of the bimetallic rim sections near their free ends. Each of these brass segments is drilled and slotted to take a single compensation screw. The steel parts of the rims are not blued. Diam. 25.0 mm, h. 2.2 mm.
Balance spring: Blued steel helical spring of large diameter with 4 turns, with terminal curves, free sprung to a brass stud on the balance cock and a bar-shaped brass collet with two holes to lighten it (see 1958,1201.1743).
Great wheel (fusee) 60 teeth
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 6 arms
Fourth pinion 8 leaves, wheel 70 teeth, 6 arms
Escape pinion 7 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Cannon pinion 14 leaves, minute pinion 18 leaves
Hour wheel 54 teeth, minute wheel 56 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1932.
(1) This watch shows so many points of similarity to the work of Robert Pennington as to justify the assumption that it was at least finished by him.
Bibliography: Vaudrey Mercer, 'The Penningtons and Their Balances', AH, Spring 1981, pp. 514-22.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Seconds hand 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.1745 (Ilbert Collection)
Previous owner/ex-collection number: M166 (Ilbert Ledger)