- Museum number
- 1958,1201.949
- Description
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MOVEMENT, DIAL AND DUST-CAP OF A LEVER WATCH.
Full-plate; fusee, Harrison's maintaining-power.
Ratchet-tooth lever-escapement, Earnshaw compensation balance, under-sprung.
Enamel dial, cream with black I-XII numerals, subsidiary seconds dial.
Hands; blued steel seconds hand, others missing except brass boss of minute hand.
Dust-cap; cut away to-make-room for set-up ratchet-wheel, click and spring.
Case missing.
- Production date
- 1845-1855
- Dimensions
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Diameter: 41.50 millimetres (dial)
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Diameter: 38.80 millimetres (dust-cap)
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Thickness: 12.30 millimetres
- $Inscriptions
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- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by John Donegan
Dublin, c. 1850
Movement of a ratchet tooth lever watch
Signature: 'DONEGAN 32 DAME ST DUBLIN' on the dial and 'John Donegan Dublin No 17494' on the back plate.
Case: Missing.
Dial & Hands: Flat dial with a sunk subsidiary seconds dial. The number '40' and a letter 'P' fired into the counter-enamel. The brass boss of the minute hand survives, the hour hand is missing. The blued-steel seconds hand survives.
Dial-plate: Not intended, the dial is pinned directly to the front plate.
Dust-cap: Elaborately pierced out to clear the set up work on the barrel bridge. Stamped SW on the inside.
Movement:
Ebauche Marks: P D 12 0
4
Frame: A full plate layout, the back plate supported by four pillars and retained by screws. A separate cock for the fusee on the front plate. The barrel bridge and the balance cock are engraved all over with scrolling foliage. The polished steel set-up ratchet and click are mounted on the barrel bridge. The number '17494' is scratched on the underside of the balance cock foot.
Fusee, Barrel and Mainspring:
Fusee: Four-turn fusee with Harrison's maintaining power, the maintaining ratchet wheel of steel.
Barrel: flanged at the cap end, internal diameter 14.9 mm, height 2.6 mm.
Mainspring: height 2.4 mm, thickness 0.25 mm.
Barrel Arbor: diameter 4.9 mm, not snailed.
Hooking: round.
Train wheels: The solid centre wheel is gilded, the third and fourth wheels are of polished brass, each with five crossings.
Jewelling: Jewelled bearings for the third wheel onwards. Those in the back plate in screwed settings. On the front plate the third wheel jewel is in a screwed setting, the rest are rubbed in. The potence has a ruby endstone in a wedge and the balance cock has a diamond endstone in a screwed setting.
Escapement: An obtuse-angle layout ratchet tooth lever escapement with short lever, single roller and D-shaped impulse pin. The enclosed pallet stones have convex impulse and locking faces. The polished brass escape wheel has three crossing.
An equal impulse escapement.
No of teeth embraced 32.
Balance & Spring: A split bimetallic undersprung balance with gold compensation and quarter screws, diameter 17.5 mm, thickness 1.15 mm. The balance is mounted 'upside down' in the watch with the cross-arm nearest the balance cock to accommodate the blued-steel flat spiral spring which has 92 turns.
Means of Regulation: A Bosley regulator registers against a divided scale with 'S' and 'F' engraved on the back plate.
Train Counts and Beat Rate:
Great wheel 72 (fusee)
Centre wheel 64 pinion 10
Third wheel 60 pinion 8
Fourth wheel 56 pinion 8
Escape wheel 15 pinion 7
Beat rate: 14,400
Motion work: cannon pinion 14
minute wheel 42, minute pinion 12
hour wheel 48
Winding System: Key wound.
Dimensions:
Movement: diameter 41.5 mm, height 12.7mm, pillar height 2.8 mm.
Provenance: Formerly in the Ilbert Collection:
- Location
- Not on display
- Condition
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Latest: 3 (2017)
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3 (1994)
- 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
- 1958,1201.949
- Additional IDs
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Previous owner/ex-collection number: CAI.0949 (Ilbert Collection)