- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Spring detent escapement.
- Production date
Diameter: 38.90 millimetres (back-plate)
Diameter: 42.50 millimetres (dial)
Thickness: 10.20 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Parkinson & Frodsham, Late 19th century
Signature: On the back plate 'Parkinson & Frodsham Change Alley LONDON 4608'. On the dial, in the upper half 'PARKINSON AND FRODSHAM LONDON'.(1)
Dial and hands: Flat enamel dial with sunk subsidiary seconds, attached to the front plate by three feet and pins. The back marked faintly in the enamel 56 and 456, the latter very faint.
The minute and hour hands missing, the seconds hand blued steel.
Ebauche marks 14, 0, 4608.
Front plate diam. 42.5 mm; back plate diam. 39.1 mm; frame h. 7.3 mm.
Frame: Typical half plate construction with three turned pillars, the back plate retained by recessed blued steel screws. A large bridge on the dial side of the front plate carries the lower bearings of the third, fourth and escapement arbors. The movement was held in its case by a hinge at the XII position and a peg set in the edge of the front plate opposite. All the brass parts gilded.
Fusee: Key wind fusee with the usual stop-work and maintaining power, the maintaining ratchet wheel steel. The setting-up-work in a shallow recess on the dial side of the front plate, the barrel arbor with an extended square on that end only. The barrel with a very slight flange on the cover end.
Going train: The usual construction but the layout unusual in that the fourth wheel is placed below instead of above the third. The brass wheels gilded, the steel pinions and arbors well finished and polished.
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. The train jewels with slightly curved faces against the pivot shoulders.
Escapement: A development of Earnshaw's spring detent escapement. The brass escape wheel with arms and rim sunk below the level of the teeth. The polished steel impulse roller with radial impulse plane. (See Charles Frodsham, registration no. 1958,1201.1833, for a very similar example.) The polished steel discharge roller without an adjusting flat, and having a wedge-shaped jewel and corresponding slot in the edge of the roller. The detent with polished top to the foot, half-round locking stone and a replacement steel passing spring held with a screw, banking by the locking stone pipe against a screw set in a brass block under the escape wheel. The foot of the detent planted inside a tangent to the locked tooth.
Balance: Bimetallic two-armed balance with gold screws, except the timing screws at the ends of the arms which are steel. Diam. of rim 15.5 mm, h. 1.77 mm.
Balance spring: Blued steel spiral spring of 9 turns with an overcoil and terminal curve, free sprung to a stud on the balance cock and a round brass collet.
Amplitude limiting device: At a certain amplitude a steel pin standing up from one balance arm will be touched by the outer coil of the balance spring and produce a braking effect.
Great wheel (fusee) 80 teeth
Centre pinion 12 leaves, wheel 80 teeth, 5 arms
Third pinion 10 leaves, wheel 75 teeth, 5 arms
Fourth pinion 10 leaves, wheel 80 teeth, 5 arms
Escape pinion 8 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection; Ilbert purchased this movement in the Caledonian Market in 1932.
(1) The firm of Parkinson and Frodsham was founded in about 1800 by William Parkinson and W. J. Frodsham, both admitted to the Clockmakers Company in 1802. At 4 Change Alley until 1842, the name appears in the 'City of London Directory' in 1873, at the same address and again in 1907 at 5 Budge Row.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Minute, hour and seconds hands missing. Fusee chain detached.
- 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.1741 (Ilbert Collection)
Previous owner/ex-collection number: M186 (Ilbert Ledger)