- Museum number
MOVEMENT AND DIAL OF A LEVER WATCH WITH SPLIT-SECONDS CHRONOGRAPH.
3/4-plate, fusee, Harrison's maintaining-power, split seconds work mounted on 4th-wheel pivot, ratchet-tooth lever-escapement, Earnshaw compensation balance.
Primitive split-seconds chronograph.
White enamel dial, hours I-XII; sunk subsidiary seconds dial.
Gold light moon hands; light blued steel seconds and split seconds hands [seconds hand with tail and hole in its end, also gold boss].
- Production date
Diameter: 40.80 millimetres (back-plate)
Diameter: 49 millimetres (dial)
Thickness: 12 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Simmons.(1)
London, c. 1875
Movement of a split seconds, ratchet tooth lever stop-watch.
Signature: On the dial 'SIMMONS LONDON' and on the back plate 'Simmons London No 12'.
Dial & Hands: A flat dial with a sunk subsidiary seconds dial. Delicate gold moon pattern hour and minute hands, blued-steel seconds hands, one with a long counter-poise, the other without a tail.
Dial-plate: Secured to the movement by five screws.
Dust-cap: None intended.
Ebauche Marks: 18 0
Frame: 3/4 plate layout, the back plate supported by three turned pillars and secured by screws. There is a separate cock on the front plate and a screwed on bush on the back plate for the fusee bearings. A separate combined cock for the escape wheel and pallets. The plain balance cock is stamped WN and scratched WN 7/76 on the underside.
Fusee, Barrel and Mainspring:
Fusee: four-turn fusee with Harrison's maintaining power, the maintaining ratchet wheel of steel.
Barrel: flanged, internal diameter 17.4 mm, height 2.45.
Mainspring: height 2.25 mm, thickness 0.25 mm.
Barrel Arbor: diameter 5.7 mm, not snailed.
Hooking: originally oval but now round.
Train: Gilded wheels, the centre, third and fourth wheels with five crossings.
Jewelling: Jewelled bearings from the third wheel onwards in the front plate, except for the pallets. The third and fourth wheel pivot holes in the back plate are un-jewelled. The escape wheel and balance with ruby endstones in screwed settings. The cock for the escape wheel and pallets with a rubbed in jewel for the escape wheel pivot.
Escapement: An obtuse-angle layout ratchet tooth lever escapement with short lever, single roller and round impulse pin. The enclosed pallet stones with convex impulse faces but flat locking faces. The gilded escape wheel has three crossings.
A mixed escapement.
No. of teeth embraced 32.
Balance & Spring: A split bimetallic balance with gold compensation and quarter screws, balance diameter 16.8 mm, thickness 1.0 mm. Blued-steel flat spiral spring with 12 turns pinned to a polished steel stud screwed to the back plate.
Means of Regulation: An index on the balance cock registers against a divided scale with 'Fast' and 'Slow'.
Train Counts and Beat Rate:
Great wheel 70 (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 12
Minute wheel 48, minute pinion 14
hour wheel 42
The split seconds device: A stop lever when pressed by a pin in the case(1) allows a spring to contact the rim of the loose seconds wheel. A loose wheel B rides on the extended seconds pivot A. On the pivot, friction tight, is arm D. The loose wheel carries a pin E and this is linked to the arm D by a hairspring, the outer end being connected to the pin and the inner end to the arm. Normally the whole assembly moves as one with the pin resting against one side of the arm. When the brake F is applied to the loose wheel the main seconds hand continues to move normally but the ancillary seconds hand stops and the pin E separates from the arm. Eventually, in just under a minute, the pin will contact the back of the arm and in this event would stop the watch. Therefore only intervals of less than a minute can be timed.
Winding System: Key wound.
Movement: diameter 49.0 mm, height 11.0 mm, pillar height 3.4 mm.
Provenance: Formerly in the Ilbert Collection. Ilbert purchased this from Malcolm Gardner 23/3/1934.
(1) Possibly made by one of the Simmons family who were in Coleman Street, London from 1815-1876.
(2) For a complete example of this type of split seconds stop-watch by Arnold and Dent see Cat. no. 109 (registration no. 1958,1201.1243).
- Not on display
Latest: 3 (2017)
- 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.1146 (Ilbert Collection)
Previous owner/ex-collection number: N218 (Ilbert Ledger)