- Museum number
MOVEMENT AND DIAL OF A LEVER WATCH FOR A BLIND PERSON.
3/4-plate; going barrel; savage type lever escapement; split bi-metallic balance.
Keyless winding and hand-set.
Engine turned silver dial with sunk subsidiary seconds.
Gold Breguet hands; seconds hand missing.
Designed for a blind person's watch.
- Production date
Diameter: 29.50 millimetres (back-plate)
Diameter: 32.70 millimetres (dial)
Thickness: 6.40 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Edward John Dent
London, c. 1850
Movement of a ratchet tooth lever watch for a blind person, the escapement with two impulse pins on the roller.
Signature: On the dial 'DENT 15430' and on the back plate 'E. J. Dent Watchmaker to the Queen London Patent No 15430'.(1)
Dial & Hands: Silver engine-turned dial with sunk subsidiary seconds, the dial retained by dog screws. Scratched '0176' on the back. This dial is probably a replacement for the original as the inscription is crude. Gold moon pattern hour and minute hands, the seconds hand missing.
Dial-plate: None intended.
Dust-cap: None intended.
Ebauche Marks: 15430 and scratched 590. The front plate is numbered 1767 on the inside next to the balance cock.
Frame: 3/4 plate layout without pillars, the front plate with machined recesses to clear the wheels. The back plate is secured by three screws. A separate disc, let into the dial side of the front plate, carries the escapement jewels. The two screw holes for the balance jewel setting have been moved, probably after manufacture.(2)
Barrel and Mainspring:
Barrel: going barrel with a recessed cover.(3) Internal diameter 12.0 mm, height 1.6 mm.
Mainspring: height 1.5 mm, thickness 0.15 mm.
Barrel Arbor: diameter 4.0 mm, not snailed.
Train: Gilded wheels, the centre, third and fourth wheels with five crossings.
Jewelling: Jewelled bearings from the fourth wheel onwards with bombé jewels for the escape wheel and pallets. Ruby endstones for the balance in screwed settings. All the other jewels are rubbed in.
Escapement: An acute-angle layout ratchet tooth lever escapement with short lever, single roller and two gold impulse pins. The enclosed pallet stones have convex impulse and locking faces. The pallets are only 6.5 mm long and are secured to the lever by a single screw. The polished brass escape wheel has three crossings.
An equal impulse escapement.
No. of teeth embraced 32.
Balance & Spring: A split bimetallic balance with gold compensation screws and platinum quarter screws. Balance diameter 12.6 mm. thickness 0.9 mm.
Blued-steel flat spiral balance spring with 10 turns pinned to a polished steel stud screwed to the balance cock table.
Means of Regulation: An index on the balance cock registers against a divided scale with 'S' and 'F' engraved on the balance cock table.
Train Counts and Beat Rate:
Great wheel 80 (barrel)
Centre wheel 64 pinion 10
Third wheel 60 pinion 8
Fourth wheel 60 pinion 8
Escape wheel 15 pinion 6
Beat rate: 18,000
Motion work: Cannon pinion 12
minute wheel 36, minute pinion 10
hour wheel 40
On the back plate there is a further minute wheel for the blind man's indication which would have been on the case back.
Winding System: Adolphe Nicole's keyless work with a further wheel meshing with the pinion on the cannon pinion arbor to drive the blind indication hand which would have been on the back of the case. The steel piece that holds the bevel winding wheel is broken and the wheel is missing.
Drive to the blind man's indication:
The rear minute wheel of 32 is driven by a pinion of 16 mounted on the cannon pinion arbor. The minute wheel has a pinion of 10 which in turn drives a wheel of 60 which is mounted at the centre. This wheel has triangular shaped teeth and carries a nib whose purpose is to drive the wheel that would have been mounted on the case back and that carried the external hour indicator, which would have indicated against touch pins.
Movement: diameter 29.8 mm height 6.5 mm, pillar height 3.9 mm.
Provenance: Formerly in the Ilbert Collection. Ilbert purchased this from Malcolm Gardner 1/1/1939.
(1) Adolphe Nicole's keyless, work for which he was granted a patent on October 14th 1844 no. 10, 348. For full details see Mercer, Dent pp. 275-279, 603, 604, plate 58 and figs. 2 & 3.
(2) For a similar basic calibre, but larger, see cat. no. 243 (registration no. 1958,1201.983).
(3) This is an early example of a recessed barrel cover which becomes more common towards the end of the 19th century.
A complete example of this type of watch by Dent exists in a private collection. It is numbered 16294 and is in an 18 carat gold open-face case hallmarked London 1851 with a maker's mark 'AN' in a rectangular cameo. The à tact indication on this watch consists of a hand set bezel that surrounds the main dial. The touch pieces are set around the case band, the one at 11 o'clock also used to set the time.
- Not on display
Latest: 2 (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.0982 (Ilbert Collection)
Previous owner/ex-collection number: Q13 (Ilbert Ledger)