- Museum number
MOVEMENT EBAUCHE OF A LEVER CHRONOGRAPH WATCH WITH CENTRE-SECONDS.
Centre-seconds fly-back chronograph.
Lever ebauche; keyless winding and hand-set.
- Production date
Diameter: 45.40 millimetres (front-plate)
Thickness: 16.30 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Maker unknown (possibly S. Smith & Son)
Switzerland, late 19th, early 20th century.
Ebauche for a centre-seconds chronograph with lever escapement.
Ebauche Marks: 1
Frame: 3/4 plate layout, the back plate supported by four turned pillars and secured by screws. There is a separate horseshoe-shaped cock for the escape wheel and pallets and one for the balance. The centre, third and fourth wheels are all recessed into the front plate, the third and fourth wheels running in a separate bridge on dial side the front plate. The back plate is recessed on the inside for the barrel. The number '22' is scratched on the edge of the thick front plate and '108765' is scratched on the train bridge beneath the dial. The edge of the front plate is still thick, having not yet been turned down to fit the case.
Barrel and Mainspring:
Barrel: going barrel with 4-turn Geneva stop work. Internal diameter 17.5 mm, height 2.3 mm.
Mainspring: not fitted.
Barrel Arbor: diameter 5.8 mm, not snailed.
Train: Brass wheels not gilded, the centre, third and fourth wheels with six crossings.
All the pivots are finished. The fourth wheel arbor is extended to carry a subsidiary seconds hand.
Great wheel 96 (barrel)
Centre wheel 80 pinion 12
Third wheel 75 pinion 10
Fourth wheel 70 pinion 10
Motion work: cannon pinion 12
minute wheel 36, minute pinion 10
hour wheel missing (would have been 40)
Similar to cat. no. 343(registration no. 1974,0401.1) with start, stop and fly-back functions indexed by a castle wheel. The fourth wheel drives a brass rocking wheel of 35 teeth carried on a pivoted frame whose tail engages with the castle wheel. Mounted on this rocking wheel is a steel fine-tooth wheel which in turn drives a centrally mounted fine-toothed brass wheel which carries the centre-seconds hand. The operation of the castle wheel engages and disengages the mesh of the two fine-tooth wheels while, at the same time leaves the rocking wheel in constant mesh with the fourth wheel. A heart-shaped cam on the centre-seconds wheel provides zeroing.
Winding System: Side set sliding pinion keyless work, the winding stem left long and unfinished.
Dimensions: Diameter 45.3 mm, height 10.0 mm, pillar height 3.25 mm.
Provenance: Purchased from J. Bennett in 1974
(1) The chronograph mechanism here is, in many respects, similar to cat. no. 343 except that here the watch is intended for a standard open-face case and here there is no minute recording mechanism.
- Not on display
Latest: 3 (2017)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number