- Museum number
Perpetual calendar watch.
Lever escapement; cam regulator adjustable from dial.
- Production date
Diameter: 43.20 millimetres
Thickness: 5.40 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Switzerland, c. 1900
Perpetual calendar watch movement with a club tooth lever escapement.
Dial and Hands: The main dial is missing but various subsidiary dials have survived; the seconds dial and the date, day and month dials. The seconds dial has dots instead of numerals and has an engine turned sunk centre. The blued steel seconds hand is still in position. The seconds dial was originally pressed into the main dial and its rim is now damaged.
Ebauche Marks: None
Frame: Bar movement, a cock for the centre wheel, one for the third and fourth wheel, another for the escape and pallets and a cock for the balance. There is a gold bridge held by three screws with a plate beneath covering the barrel ratchet wheel. The movement was located in the case by a peg and retained by two screws.
Barrel and Mainspring: (see note). Geneva stopwork with 4 turns.
Going barrel I. diameter approx 16.5 mm.
Mainspring: height approx 1.0 mm, thickness approx 0.20 mm.
A brace for the mainspring.
Train: Was a high quality train. The gilded brass centre, third and fourth wheels with 5 crossings, the steel escape wheel with 4 crossings.
Jewelled: At the centre in the back plate and from the third onwards, all the jewels rubbed in and bombé. The escapement with ruby endstones throughout.
Escapement: Conventional club tooth lever escapement with a straight line layout, a double roller with a triangular impulse stone. A long lever with a poising tail to the pallets, the dart screwed on. The pallet jewels exposed, the acting faces flat. A recessed escape wheel.
An equidistant locking escapement.
No of teeth embraced 3 ½.
Balance and Spring: A bimetallic balance with some gold and some platinum screws. Gold quarter screws. Balance diameter 14.0 mm., height 0.6 mm. Blued-steel flat spiral spring with 16 turns and a terminal curve.
Means of Regulation: Micrometer regulator for the index mounted on the balance cock. The operating cam missing. There was originally an indication on the dial, the rack and pinion for this is still in position.
Train Counts and Beat Rate:
Great wheel (barrel) Could not be determined.
Centre wheel 80 pinion 10
Third wheel 75 pinion 10
Fourth wheel 70 pinion 10
Escape wheel 15 pinion 7
Beat Rate: 18,000
Motion Work: cannon pinion 12, minute wheel 36
minute pinion 10, hour wheel missing.
Winding System: Keywound with a male key.
Continuous Perpetual Calendar Work: This is laid out in an unusual manner being partly on one side of the front plate and partly on the other. The month wheel rotates in 4 years and unusually has the moon dial at its centre. The movement is a very flat example for one containing this complication, being a mere 5 mm in thickness when measured over the plates.
For details of perpetual calendar work see Appendix 0-0.
Dimensions: Movement diameter 43.6 mm., height 6.4 mm.
Provenance: Not known.
Note: This watch has been in a fire, a fire of sufficient severity to soften all the steel work in the movement. It has only be practicable to dismantle part of the movement, the risk of damage to the remainder being too great to compensate for the extra information gained.
- Not on display
Latest: 3 (2017)
4 (Feb 1995) probably fire-damaged
- Britain, Europe and Prehistory
- Registration number