- Museum number
- 1958,1201.1738
- Description
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SILVER-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT.
Chronometer watch.
Spring detent escapement.
Enamel dial.
Silver case.
- Production date
- 1810 (case)
- Dimensions
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Diameter: 54.70 millimetres (case)
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Diameter: 48.40 millimetres (dial)
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Thickness: 24.70 millimetres
- $Inscriptions
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- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Robert Pennington (Camberwell 1780-1816)
Chronometer
Signature: On the barrel bridge 'Pennington London 130/596.'
Case: Plain silver consular case with the London hallmark for 1810 and the maker's mark T.G. Diam. 54.8 mm, h. over glass 24.3 mm.
Dial and hands: Flat enamel dial, the minute and second divisions appear to be engine divided with a scribing point under the enamel markings. Attachment of the dial to the dial plate by three short feet and pins.
Blued steel hands, the hour and second hands replacements, the minute hand possibly original.
Movement:
Dial plate diam. 48.5 mm; front plate diam. 47.0 mm; back plate diam. 42.5 mm; frame h. 8.5 mm.
Frame: Full plate with detachable barrel bridge, four turned pillars, the back plate retained by pins. On the inside of the front plate 596. The dial plate attached to the front plate by three short pillars and pins. On the inside of the dial plate scratched 596. No provision for a case catch or hinge, the movement secured in its case by a radial peg in the edge of the dial plate at IX and a screw opposite. The brass parts gilded, little having found its way onto the front plate under the dial or inside the dial plate. A large dust-excluding pipe with oval foot of characteristic shape around the winding square. The balance potence with a shaped foot without the usual moulded edge.
Fusee: Keywind fusee with the usual stop-work. The maintaining power with brass ratchet wheel and a combined detent and return spring. The setting-up-work in a shallow sink on the front plate under the dial. The barrel arbor with an extended square at both ends, a brass setting-up ratchet wheel. The barrel without a flange at the cover end.
Going train: Well made and finished, the brass wheels gilded, the pinions and arbors polished.
Jewelling: The fourth arbor lower pivot in a pierced jewel, and those of the escapement in pierced jewels with endstones. A diamond endstone in a blued steel ring on the balance cock. The heads of the screws holding the balance lower bearing are filed away so that the bearings can be removed if they are undone half a turn.
Escapement: A development of Earnshaw's spring detent escapement. The very light gilded brass escape wheel with arms and rim sunk below the level of the straight-backed teeth. The steel impulse roller polished all over and with a radial impulse face. The steel discharge roller with a wedge-shaped jewel dovetailed in place, no flat for adjusting. The remains of the much repaired dovetailed detent set in a gilded brass block with an integral arm for the banking screw. The block screwed and steady pinned to the underside of the back plate, so that the axis of the detent lies inside a tangent to the locked tooth. The detent is banked by an eccentric screw in the side of the brass block limiting the movement of the detent foot towards the balance. A steel passing spring riveted on with one rivet.
Balance: Bimetallic two-armed balance with red-gold compensation and quarter screws, probably a replacement for the original Pennington balance (see registration no. 1958,1201.1743). Diam. 24.2 mm, h. 24.2 mm.
Balance spring: Duo-in-uno blued steel spring with an upper terminal curve, free-sprung to a brass stud on the balance cock and to a steel collet, probably fitted with the new balance.
Amplitude limiting device: Consisting of two pins set vertically in the balance arms, one on each side of the spring, limiting the free expansion of the balance spring if the amplitude increases beyond a certain limit.
Going-train counts:
Great wheel (fusee) 60 teeth
Centre pinion 12 leaves, wheel 75 teeth, no crossings
Third pinion 10 leaves, wheel 64 teeth, 5 arms
Fourth pinion 8 leaves, wheel 70 teeth, 5 arms
Escape pinion 7 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Motion work:
Cannon pinion 12 leaves, minute pinion 16 leaves
Hour wheel 48 teeth, minute wheel 48 teeth
Provenance: Ilbert collection; purchased by Ilbert from Ash in 1932.
Bibliography: Vaudrey Mercer, 'The Penningtons and Their Balances', AH, Spring 1981, pp. 514-22.
- Location
- Not on display
- Condition
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Latest: 3 (2017)
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4 (Oct 1995) Screw to secure movement in case broken off in hole.
- Acquisition date
- 1958
- 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.
- Department
- Britain, Europe and Prehistory
- Registration number
- 1958,1201.1738
- Additional IDs
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Previous owner/ex-collection number: CAI.1738 (Ilbert Collection)
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Previous owner/ex-collection number: M111 (Ilbert Ledger)
