- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH ROBIN TYPE LEVER ESCAPEMENT.
Lever escapement; `Robin' type.
- Production date
Diameter: 41.90 millimetres (back-plate)
Diameter: 44.70 millimetres (dial)
Thickness: 11.70 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Maker Unknown, c. 1860
Watch Movement with Robin Type Escapement
Signature: On the back plate 'Union Patent 2291'.
Dial and hands: Flat enamel dial, slightly damaged, with sunk subsidiary seconds, and signed in the upper half 'Union Patent 2291', attached to the front plate by three feet and pins. The back of the dial marked B and 91 (see registration nos 1958,1201.1832; 1958,1201.1830 and 1958,1201.1828). Gold minute and hour hand, blued steel seconds hand.
Ebauche marks: H.F., 16 2 2291 (see registration nos 1958,1201.1832; 1958,1201.1830 and 1958,1201.1828). Both on the underside of the balance cock foot and on the plate under the foot a c embracing an o; most of the frame parts are marked 91.
Front plate diam. 44.4 mm; back plate diam. 42.0 mm; frame h. 7.2 mm.
This movement, apart from being slightly smaller, resembles that of a Patent Union Chronometer, the most obvious point of similarity being the shape of the fourth and escape wheel bridge. There are, however, the following detailed differences:
The fourth wheel is fixed to the other end of its pinion and so is above the third and centre wheels, and there is no sink for it in the front plate. The centre wheel is not crossed out, and the pinion is solid and not drilled for the hand-set arbor.
There is a movement hinge, and a case catch and spring on the dial side of the front plate, and the train and escapement bridge is divided in two and finished to a different shape.
The train pivot not jewelled, only the pivots of the escapement in pierced jewels. The endstone in the balance cock of ruby.
Fusee with five turns, normal maintaining power, steel maintaining ratchet wheel.
Escapement: The brass escape wheel has only a single set of teeth, for both locking and impulse. This is an inferior arrangement to that of the Patent Union Chronometer because oil applied to the pallets will inevitably find its way onto the impulse jewel and spoil the rate. The patent of 1863 corrected this fault.(1) The pointed lever arm top pivot runs in an adjustable cock, as in registration nos 1958,1201.1830 ; 1958,1201.1742 and 1958,1201.1828. The ruby roller on the balance staff is made of brass and could be a later replacement. The escape wheel is not sunk out for lightness.
Balance: Bimetallic two-armed balance with brass compensation and quarter screws. Diam. 16.1 mm, h. 1.1 mm.
Balance spring: Blued steel flat spiral spring of 14¾ turns with an overcoil and terminal curve, pinned to a polished steel stud on the balance cock and a round brass collet.
Great wheel (fusee) 72 teeth
Centre pinion 10 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 8 leaves, wheel 63 teeth, 5 arms
Escape pinion 7 leaves, wheel 15 teeth, 3 arms
Beats per hour: 16,200
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, minute wheel 36 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Malcolm Gardner in 1930.
(1) A search of the patent records has not revealed a patent corresponding exactly with this escapement. It is therefore assumed that it is an improvement on the original patent no. 233 of 1859 and preceded that protected by No. 2184 of 1863.
- Not on display
Latest: 4 (2017)
4 (Oct 1995)
- 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.1829 (Ilbert Collection)
Previous owner/ex-collection number: M318 (Ilbert Ledger)