- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH PIVOTED DETENT ESCAPEMENT, KEYLESS WOLF-TOOTH WINDING AND PLATE IN SHAPE OF DOUBLE-HEADED EAGLE.
Pivoted detent escapement; 3/4 plate as double eagle, gold train.
Diameter: 45.80 millimetres (dial)
Thickness: 10.60 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Ami Sandoz and Son, Switzerland, Late 19th century
Signature: On the dial 'Ami Sandoz & Son No. 90964'.
Dial and hands: Flat enamel dial with sunk subsidiary seconds. Marked on the reverse 90964. Two dial feet pass through the pillar plate and are retained by two screws.
The hour hand broken, the minute and seconds hands blued steel with gilding; unusual tail to the seconds hand.
Ebauche marks 90964.
Front plate diam. 45.1 mm; frame h. 7.8 mm; front plate th. 2.80 mm reduced to 1.55 mm.
Frame: A type of three-quarter-plate construction with three turned pillars. The back plate is pierced and engraved in the form of an Imperial Russian double-headed eagle holding an orb and sceptre in its claws and retained by recessed blued steel screws. The front plate with separate subplates under the dial for the lower bearings of the barrel arbor and those of the fourth and escapement arbors. The movement was retained in its case by a peg and two dog screws on the edge of the front plate. The frame made of nickel brass with gilded decoration in the engraving, the front plate with a sunray pattern on the inner surface.
Going barrel and keyless work: The going barrel of nickel brass, with four-turn Geneva stop-work on the cover end. Sliding pinion type of keyless work; hand setting operated by a push-piece in the band of the case. The transmission gearing for winding with 'Wolf tooth' form. The mainspring marked 'J. Robert', probably the original spring. The winding arbor in two parts, the part remaining in the frame with a squared hole for the now missing pendant.
Going train: Wheels of red gold, burnished flat on both sides. The pinions and arbors well finished and polished, the centre pinion hollow for the arbor carrying the cannon pinion.
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 polished steel ring on the balance cock. An extra non-functional decorative endstone in a screwed setting on one of the eagle's heads on the back plate, to balance the pierced jewel on the other.
Escapement: Pivoted detent escapement with the escape wheel locked on the second tooth after the one which has just given impulse. The red gold escape wheel lightly crossed out, and with the arms sunk below the level of the rim and teeth. The polished steel impulse roller with a jewel leaning slightly towards a radial to the tip. The steel discharge roller with a straight-sided slot for the jewel and two crescent-shaped grooves for adjusting, only the edge polished.
The pivoted detent with spiral return spring, gold passing spring, the end of the horn formed at right angles to the rest to hold the passing spring clear of the detent. Banking against the lower extension of the half-round locking stone against a flat on the edge of the head of a screw in a recess in the escapement bridge.
Balance: Two-arm compensation balance with brass screws. Diam. 18.0 mm, h. 16.0 mm.
Balance spring: Blued steel helical spring of 7 turns, with terminal curves, free sprung to a stud clamped to the balance cock and a narrow bar-shaped nickel collet with a boss on the balance staff.
Great wheel (going barrel) 78 teeth
Centre pinion 10 leaves, wheel 80 teeth, 5 arms
Third pinion 10 leaves, wheel 75 teeth, 5 arms
Fourth pinion 10 leaves, wheel 70 teeth, 5 arms
Escape pinion 7 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, minute wheel 36 teeth.
Provenance: Ilbert Collection; purchased by Ilbert from Webster in 1931.
- Not on display
Latest: 3 (2017) Dial chipped at VIII
4 (Oct 1995) Hour hand broken at boss.
- 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.1750 (Ilbert Collection)
Previous owner/ex-collection number: L10 (Ilbert Ledger)