- Museum number
SILVER CASED CENTRE-SECONDS POCKET-CHRONOMETER WITH PIVOTED DETENT ESCAPEMENT.
Independent centre-seconds pocket chronometer.
Front plate with separate cocks; going-barrels; independent centre seconds.
Arnold pivoted detent escapement; bimetallic compensation balance.
White enamel dial, hours 1-12; secret signature.
Blued steel hands.
Silver case, numbered 3919, 5730, 84, maker's mark. Inscription on the cuvette.
- Production date
- 1822-1838 (case)
Diameter: 58.20 millimetres (case)
Diameter: 47.60 millimetres (dial)
Thickness: 19 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Amaury No. 11995
Signature: Engraved on the cuvette 'Amaury AU HAVRE DE GRACE no 11995' with an arrow through the top of the N; and the inscription: 'Echapement a la Arnold garni en pierres, 10 joy'x, balancier compense' (Arnold-type escapement, ten jewels, compensated balance).(1)
Case: Open face silver case with the No. 3919 and 5730, also 84 and the maker's mark MF. The French quality control mark for 1822-38. The middle of the case finely engine-turned. Slide to operate independent seconds mechanism at 6 o'clock. Front and back hinged. The movement fitted into a gilded brass drum to which the cuvette is hinged. This drum fitting into the case from the back and held by three radial screws on the edge of the dial. Diam. 58 mm, th. 18.4 mm.
Dial and hands: Curved enamel dial, slightly cracked. Arabic numerals. Secret signature 'Amaury au Havre' across the lower half of the dial in fine cursive script.(2)
Blued steel moon minute and hour hands and independent sweep centre seconds hand set between them.
No ébauche marks, but the number 11995 stamped on the front plate under the dial.
Front plate diam. 49.3 mm; front plate th. 2.05 mm; frame h. 9.0 mm.
Frame: A nicely gilded brass frame made up of a massive front plate and a number of separate cocks screwed to it with blued steel screws. The going-train wheel carried on the back and the independent seconds train under the dial with the motion work. Two hanging barrels with a type of Geneva stop-work, one for each train, key winding.
Going train: Brass wheels not gilded but carefully made and crossed out, the top and bottom surfaces finished by flat burnishing or polishing. Steel pinions well polished. The fourth wheel pivot on the dial side extended so that it could have carried a subsidiary seconds hand.
Independent seconds train: Consisting of a great wheel integral with the smaller going barrel and four wheels and five pinions. The third of these wheels, on its large diameter pinion, running free on the cannon pinion and carrying the long independent seconds hand, the gear ratio between this wheel and the last pinion of the train is 60:1. The last pinion carries a small arm or flirt arranged to intersect a five-leaf pinion on the arbor of the escape pinion. A slide in the band of the case operates a level which releases the flirt. When the flirt is released it intersects the five-leaf pinion and is so positioned that it is released as each leaf of the pinion passes, that is nearly a turn at every sixth swing of the balance, or one second. As the flirt turns slowly forward against the pinion leaf the long seconds hand advances accordingly in jumps of almost a second, the completion of the whole of the seconds motion takes place at the instant of the next release. The seconds hand can be prevented from advancing if the slide is moved so that the flirt is held up. There is no means of setting the independent seconds hand to zero except by stopping it at that point. This system was superseded later in the nineteenth century by the invention of the chronograph mechanism.
Jewelling: The pivots of the fourth wheel of the going train and the escapement run in large well-made jewels either clear, or of a pale purple colour. Endstones are fitted for the balance. All the other pivots run in brass holes.
Escapement: A polished steel escape wheel with finely pointed inclined teeth and two pivoted detents. The escape wheel locked by the detent nearest to it which carries a jewel for the purpose and has a pivoted ruby roller on an arm. Unlocking is achieved by the other detent which has two arms, one in the path of the unlocking pallet on the balance staff, the other arm to contact the pivoted ruby roller on the first detent. Both detents are returned, the first against a stop, the second against the first, by spiral springs.
Impulse is given directly to a pallet on the balance staff by the escape wheel teeth.
Balance and balance spring: Blued steel spiral balance spring of 6 turns pinned to a steel stud on the front plate. A grained steel index with a tail moving over an engraved sector on the balance cock and 2 brass pins embracing the first turn of the balance spring. The index is held under a grained steel endstone plate.
Brass and steel bimetallic balance having a single crossbar. The segment compensation weights on the bimetallic rims with micrometric adjustment by a squared worm. This worm is in the body of the weights acting in a half thread form cut in the outside of each rim. Registration dots on the rims at each ninth turn. Diam. 17.5 mm, h. 1.29 mm.
Great wheel (barrel) 96 teeth 3 turn stop-work
Centre pinion 10 leaves, wheel 64 teeth, 5 arms
Third pinion 8 leaves, wheel 60 teeth, 5 arms
Fourth pinion 8 leaves, wheel 72 teeth, 5 arms
Escape pinion 6 leaves, wheel 15 teeth, 4 arms
Beats per hour: 21,600
Independent seconds train:
Barrel 75 teeth, 4 turn stop-work
First pinion 10 leaves, wheel 64 teeth, 5 arms
Second pinion 8 leaves, wheel 75 teeth, 5 arms
Centre pinion 10 leaves, wheel 60 teeth, 5 arms
Fourth pinion 6 leaves, wheel 36 teeth, 4 arms
Flirt pinion 6 leaves
Cannon pinion 10 leaves, minute pinion 12 leaves
Hour wheel 36 teeth, minute wheel 40 teeth
The hour wheel crossed out with four arms. The motion work gearing has a coarser pitch than the wheels of the independent seconds train.
Provenance: Ilbert Collection; purchased by Ilbert from Mal¬colm Gardner in 1936.
(1) Tardy 1971 gives Amaury as end of 18th century.
(2) Secret signatures are only normally associated with A. L. Breguet.
- Not on display
Latest: 3 (2017)
3 (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.1837 (Ilbert Collection)
Previous owner/ex-collection number: P81 (Ilbert Ledger)