- Museum number
Spring detent escapement with Arnold-type escape wheel, Earnshaw balance; fusee with Geneva stopwork.
- Production date
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Urban Jürgensen (1776-1830), Danish c. 1820
Signature: On the back plate and on the dial URBAN JÜRGENSEN
Dial and hands: Flat enamel dial with small sunk subsidiary seconds dial. Canister dial with a positioning peg.
Blued steel minute and hour hands, seconds hand missing.
Ebauche marks UI under a crown and 424.
Front plate diam. 49.1 mm; back plate diam. 47.4 mm; frame h. 8.7 mm.
Frame: A type of three-quarter plate construction built up on a massive front plate, and without a dial plate. Four conical turned pillars, the back plate retained by marked blued steel screws. Detachable crescent-shaped barrel bridge. The movement retained in its case by two polished steel dog screws in the front plate, and a positioning peg. The various bridges and cocks without screwdriver slots to aid their removal during dismantling. All the brass parts nicely gilded.
Fusee: Fitted with Harrison maintaining power, steel ratchet wheel and pivoted maintaining detent, with its return spring on the inside of the front plate, the tail under the balance. A modified six-turn Geneva stop-work fitted on the front plate under the dial with the setting-up-work. The barrel arbor with an extended square on the front plate end only.
Going train: The centre wheel snailed on both sides not gilded, all the other wheels gilded. The steel arbors well polished and finished. An unusual train count is used with a fourth wheel of 54 teeth giving 16,200 beats per hour of the balance.
Jewelling: The third, fourth and escape wheel arbor pivots in pierced jewels with flat faces against the pivot shoulders. The balance pivots in pierced jewels with endstones, a diamond endstone in the balance cock, set in a blued steel ring.
Escapement: Spring detent escapement of basically Arnold design. The brass escape wheel with cycloidal impulse faces to the teeth. Steel detent and passing spring, the foot of the detent screwed and steady pinned to a gilded brass arm passing round the fourth wheel sink on the edge of the front plate. An adjusting screw in the end of the brass arm acting on a steel pillar can be used to move the detent towards or away from the balance centre. The detent banked against a brass screw with steel clamping screw set in a brass piece screwed and pinned to the front plate. The locking stone of rectangular section with one short side rounded, and set in a hole in the detent of exactly matching shape. The steel impulse roller with radial face to the pallet and sharp corner to receive impulse. Large oval counterpoising hole opposite the impulse pallet. The usual jewelled discharge roller between the impulse roller and the balance. The escapement is set up so that the escape wheel teeth have a heavy drop on at the beginning of impulse, which has resulted in the impulse faces of the teeth being cut where they have met the corner of the impulse pallet. (C.f. other watches with this type of detent escapement, especially those by the Arnolds, father and son.)
Balance: Bimetallic two-armed balance with brass seg¬ment weights held by steel screws from underneath, and with steel timing screws at the ends of the arms. The steel parts of the balance do not appear to have been hardened and tempered. Diam. 19.5 mm, h. 2.3 mm.
Balance spring: Blued steel helical spring of 6½ turns, with terminal curves. Poised steel collet on the balance staff, adjustable overhanging stud fixed to the back plate as used by John Arnold.
Amplitude limiting device: The basic design similar to that used by the Brockbanks. A pivoted arm is acted on by the balance spring and caused to move into the path of a stud on one balance arm, when the amplitude increases beyond a certain value and before the escapement unlocks twice with the balance turning in the same direction. With the balance spring as fitted the device cannot work, the diameter of the spring being too small. This suggests that the balance spring is a later replacement of smaller diameter than the original.
Going-train counts: Great wheel (fusee) 84 teeth
Centre pinion 14 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 8 leaves, wheel 54 teeth, 4 arms
Escape pinion 6 leaves, wheel 15 teeth, 4 arms
Beats per hour: 16,200
Cannon pinion 12 leaves, minute pinion 18 leaves,
mounted on a tube on the minute wheel
Hour wheel 48 teeth, minute wheel 54 teeth
Provenance : Ilbert Collection, purchased by Ilbert from Gardner in 1932.
- 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.1605 (Ilbert Collection)
Previous owner/ex-collection number: M299 (Ilbert Ledger)