- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement.
- Production date
Diameter: 40.50 millimetres (back-plate)
Diameter: 48.30 millimetres (dial)
Thickness: 19.10 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Stephenson and Farrow, c. 1820
Signature: On the barrel bridge 'Stephenson and Farrow LONDON 1073'. On the dial STEPHENSON AND FARROW LOMBARD ST.(1)
Dial and hands: Flat enamel dial, attached by a peg and screw in the edge of the dial passing into holes in the short flat dial feet. The circle and divisions marked and divided with a scriber. On the dial STEPHENSON AND FARROW LOMBARD STREET.
Gold minute and hour hands, the seconds hand missing.
Dial plate diam. 48.3 mm; front plate diam. 42.1 mm; back plate diam. 40.9 mm; frame h. 8.5 mm.
Frame: Full plate construction with four turned pillars, two having provision for pins and two for blued steel screws to retain the back plate. A detachable barrel bridge. No dust cap or ring or provision for one. The dial plate carrying the movement hinge secured to the front plate by three countersunk headed screws under the dial. The case catch and hinge mounted on the front plate under the dial. Note that the dial plate is considerably wider than the front plate, and compares with Earnshaw watches registration nos 1958,1201.1953 and 1958,1201.1732. All brass parts gilded.
Fusee: Keywind fusee without provision for a dust guard round the winding square. The usual stop-work and maintaining power, with a steel maintaining ratchet wheel; and the maintaining detent return spring a short piece of wire set in a screw pointing down from the back plate and passing into a small hole in the detent. Setting-up-work on the front plate under the dial, the barrel arbor with an extended square on that end only. The barrel without a flange.
Going train: Well-made and finished conventional train and layout. The brass wheels gilded, the steel pinions and arbors well finished and polished. The centre pinion with turned and polished undercuts on both sides.
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, those of the escapement with endstones. A diamond endstone set in a blued steel ring on the balance cock.
Escapement: A typical Thomas Earnshaw detent escapement except for the dovetailed detent. The brass escape wheel with arms sunk out below the level of the rim and teeth, and tooth form of characteristic shape and finish. The top and bottom of the wheel with polished or burnished finish. The steel impulse roller with polished bottom, edge and shallow v-shaped notch. The impulse surface leaning towards a radial to the tip. The usual jewelled polished steel discharge roller.
The dovetailed detent held by a single screw in a brass block, with an adjusting screw for the movement of the detent towards or away from the balance axis. An integral arm carries a banking screw in a slotted hole, banking the detent against the end of the threaded part of the screw. The remains of the detent with a gold passing spring riveted on, and a half-round ruby locking stone, possibly all a replacement for the original.(2)
Balance: Typical Thomas Earnshaw bimetallic balance, see registration no. 1958,1201.1732. The steel part of the rims blued, brass segment weights secured by screws from the inside, and blued steel cross-arms to limit the inward movement of the rims with brass pegs set in the weights passing into rings on the ends of these blued steel arms. The central boss joining the arms sandwiched between the balance and brass pins driven into the brass collet on which the balance is mounted. Brass timing screws set in the rims at the ends of the arms. Diam. of rim 18.4 mm, h. 2.9 mm.
Balance spring: Blued steel helical spring of 6 turns, with terminal curves, free sprung to a polished steel stud on the balance cock and a shaped brass collet.
Great wheel (fusee) 62 teeth
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 8 leaves, wheel 70 teeth, 5 arms
Escape pinion 7 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 16 leaves
Hour wheel 48 teeth, minute wheel 48 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Malcolm Gardner in 1931.
(1) Britten 19S2 lists D. W. Stephenson and J. Farrow 1820-3 at 27 Lombard St, London, and Stephenson and Farrow 1810-24 at the same address.
(2) It seems likely that the escapement and balance were made by Thomas Earnshaw sen. or jun.
- Not on display
Latest: 3 (2017)
4 (Oct 1995) Seconds hand missing. Detent broken. (?)Balance arbor damaged.
- 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.1751 (Ilbert Collection)
Previous owner/ex-collection number: M287 (Ilbert Ledger)