- Museum number
POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT.
Repeating chronometer watch.
Spring detent escapement; duo-in-uno spring.
- Production date
Diameter: 39.50 millimetres (back-plate)
Diameter: 45.30 millimetres (dial)
Thickness: 12.50 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Charles Frodsham, c. 1867
Signature: On the back plate 'Chas Frodsham 84 Strand LONDON AD Fmsz N° 03503'. On the dial 'CHAs FRODSHAM No. 03503 AD F.m.s.z.'.
Case: No case but was open face.
Dial and hands: Flat enamel dial with sunk subsidiary seconds retained in the front plate recess by two feet, and screws going into the edge of the front plate. Accurate positioning of the dial ensured by pegs on either side of each dial foot set inside the rim of the front plate.
Blued steel hands, minute hand missing, seconds hand a replacement.
Front plate diam. 45.3 mm; back plate diam. 39.8 mm; frame h. 8.9 mm.
Frame: Three-quarter plate with four turned pillars, the back plate retained by blued steel screws whose threads do not correspond with those of registration no. 1958,1201.1598, otherwise movement similar. The front plate deeply recessed for the repeating and motion work under the dial. All the brass parts gilded. The movement was retained in its case by a single peg in the edge of the front plate and a screw opposite passing through the case middle and into the front plate, on the edge of the dial.
Fusee: Keywind fusee, with normal stop-work and maintaining power. The maintaining ratchet wheel steel. The polished steel setting-up-work with click spring on the back plate, the barrel arbor squared at both ends.
Going train: Apart from a larger great wheel with more teeth, the train is very similar to that of 1958,1201.1598 with high numbered pinions, well finished, and lightly crossed out gilded wheels, all with a square-bottomed tooth form.
Jewelling: All the pivots of the going train and escapement arbors in pierced jewels, the fourth, upper and escapement with endstones, all in screwed settings. The repeating runner pivots, without exception, in plain holes in the frame.
Escapement: A development of the Earnshaw detent escapement. The escape wheel brass, the remains of the detent mounted on a lyre-shaped polished steel frame carrying the banking screw (see also 1958,1201.1598). The polished steel impulse roller not jewelled, but with radial impulse face. The discharge roller jewelled, and with a flat for adjusting.
Balance: Bimetallic two-armed balance with gold compensation screws and quarter nuts on steel studs set in the rim. Diam. 16.0 mm, h. 1.49 mm.
Balance spring: Blued steel duo-in-uno spring with a terminal curve free sprung to a steel stud on the balance cock. Polished steel collet. (See registration no. 1958,1201.1833for a similar spring.)
Minute repeating work: Of Swiss design if not manufacture, and showing many points of similarity with that of 1958,1201.1598, including the surprise piece constantly acting on the minute cam flirt.
Great wheel (fusee) 84 teeth
Centre pinion 12 leaves, wheel 80 teeth, 6 arms
Third pinion 10 leaves, wheel 75 teeth, 6 arms
Fourth pinion 10 leaves, wheel 80 teeth, 6 arms
Escape pinion 8 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
First wheel 50 teeth, pinions all six leaves each
Second wheel 40 teeth
Third wheel 34 teeth
Fourth wheel 30 teeth
Fifth wheel 30 teeth
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, minute wheel 36 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Contarde in 1937.
Bibliography: Mercer 1981.
- Not on display
Latest: 2 (2017)
2 (Oct 1995) Dial severely chipped at edge.
- 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.1599 (Ilbert Collection)
Previous owner/ex-collection number: P150 (Ilbert Ledger)