- Museum number
MOVEMENT AND DIAL OF A LEVER CHRONOGRAPH WITH CENTRE-SECONDS.
3/4-plate movement; going barrel; gold train wheels; club-tooth lever escapement; gold escape wheel, split bi-metallic balance, balance spring with overcoil.
Cam and fork regulator; fly back chronograph.
White enamel dial with sunk subsidiary seconds and 1/5th seconds around the outside.
- Production date
Diameter: 42 millimetres (dial)
Thickness: 12.30 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by American Waltham Watch Co.
Massachusetts, U.S.A., c. 1885
Chronograph watch movement with club tooth lever escapement.
Signature: On the dial 'A.W Co WALTHAM'. On the back plate 'A.W. Co. WALTHAM MASS 2719968 Pat. Sept. 28. 80 Eng No. 32241 Safety Pinion'.
Dial and Hands: Flat dial with sunk subsidiary seconds. Around the minute circle is marked seconds and fifths of seconds numbered 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275 and 300. In the counter enamel, in red, is 12 showing where this is to come on the front. Blued-steel spade hands and blued-steel centre seconds and small seconds hands.
Ebauche Marks: 19968
Frame: Nickel silver frame spotted all over, 3/4 plate construction, a separate bridge for bottom pivots of the centre seconds wheel and the escape wheel. The pallet cock engraved, under this and the balance cock is stamped 19968.
Barrel and Mainspring: Both the going barrel and its cover are stamped 19968. Barrel I. diameter 17.0 mm., height 2.5 mm.
Mainspring: height 2.2. mm., thickness 0.22 mm.
Arbor: diameter: 5.3 mm., snailed.
Hooking: T piece.
Train: The wheels are gold with five crossings except for the escape wheel which has four. A high quality train.
Jewelled: From the third onwards, those on the back plate in screwed gold settings, those in the front plate rubbed in except for that at the balance which has a screwed setting. Ruby endstones for the balance pivots.
Escapement: A club tooth lever escapement, straight line layout, short lever, single roller, D shaped impulse stone. Gold escape wheel, the teeth not chamfered. Two part steel pallets with conterpoised end, convex impulse face to the exposed stones. An equal impulse escapement.
Number of teeth embraced 3½.
Balance and Spring: A split bimetallic balance with gold compensation and quarter screws. Balance diameter 15.3mm., thickness 1.2 mm. Blued-steel flat spiral spring with terminal curve and 16 turns.
Means of Regulation: Micrometer regulated index on the balance cock. The index with a forked tail which embraces an eccentrically mounted cam; a protruding tail on this registers against a divided semi-circular scale with engraved 'F S'.
Train Counts and Beat Rate:
Great wheel (barrel) 85
Centre wheel 80 pinion 12
Third wheel 75 pinion 10
Fourth wheel 80 pinion 10
Escape wheel 15 pinion 8
Beat Rate 18,000
Motion work cannon pinion 12, minute wheel 36
minute pinion 10, hour wheel 40
Winding System: Side lever set rocking bar keyless work.
Chronograph Work: A flat edge cam controls levers which give the three conditions run, stop and return to zero. The centre seconds wheels is pushed upwards into engagement with ancillary third wheel. In the running condition the engaging teeth are fine serrations on a chamfered edge.
Dimensions: Movement diameter: 42.1 mm., height 12.4 mm.
Provenance: Formerly in the Ilbert collection. Ilbert purchased this watch movement 3/10/1936 from Malcolm Gardner.
The Patent was taken out by L.A. Groth on August 6th 1880. It covers the chronograph work.
- 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.0903 (Ilbert Collection)
Previous owner/ex-collection number: P94 (Ilbert Ledger)