- Museum number
SUBSIDIARY SECONDS POCKET-CHRONOMETER MOVEMENT WITH PIVOTED DETENT ESCAPEMENT.
Pivoted detent escapement.
- Production date
Diameter: 41.70 millimetres (back-plate)
Diameter: 44.70 millimetres (dial)
Thickness: 12.20 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by P. Norris; Second half of the 19th century
Signature: On the back plate 'P. Norris Liverpool no 5421'.
Dial and hands: Flat enamel dial with sunk subsidiary seconds, attached to the front plate by three feet and pins. On the back of the dial, in the enamel, the number 12 in green. Blued steel hands.
Ebauche marks 16*1 5421 C.S.
Front plate diam. 44.8 mm; back plate diam. 41.9 mm; frame th. 7.9 mm.
Frame: Half plate construction with three turned pillars, the back plate retained by recessed blued steel screws. The movement held in its case by a hinge at XII o'clock and a peg in the edge of the front plate opposite. All the brass parts gilded.
Fusee: Keywind fusee, with the usual stop-work and maintaining power, the maintaining ratchet wheel steel. The setting-up-work under the dial in a shallow recess on the front plate. The barrel arbor with an extended square on that end only.
Going train: The centre arbor hollow for the squared hand-set arbor carrying the cannon pinion. The brass wheels with a burnished finish on both sides and not gilded. The steel pinions well finished and polished.
Jewelling: The pivots of the third, fourth and escapement arbors in pierced jewels, those of the escape wheel and balance staff with endstones.
Escapement: An unusual pivoted detent escapement, the rather heavy brass escape wheel not sunk out for lightness. The detent integral with a square boss on its arbor. The boss drilled and fitted with two leaf springs, one to provide passing action and made of a material resembling gold, the other of steel and acting as the return spring, its end bearing on a pin set in the fourth arbor cock. Banking for the detent provided by a brass piece partly concentric with the balance staff contacting the locking stone boss, there is no adjustment for the depth of locking. The locking stone itself a half-round jewel.
The usual jewelled, polished steel discharge roller, without an adjusting flat, fitted between the impulse roller and the balance. The steel impulse roller not jewelled and with a polished impulse face leaning towards a radial to the tip. The edge and bottom and the roller also polished as well as both sides of the impulse notch, which ends in a hole in the roller to enable the balance to be removed without disturbing the detent.
Balance: Bimetallic two-armed balance with gold screws and quarter screws. Diam. 16.8 mm, h. 1.79 mm.
Balance spring: Blued steel helical spring of 6¾ turns, with terminal curves, free sprung to a polished steel stud on the balance cock and a brass, poised collet.
Great wheel (fusee) 78 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
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 1933.
Note: The ébauche appears to have been originally intended for a spring detent escapement, filled holes around a sink concentric with the balance staff indicate where the spring detent banking would have been. The alterations and additions for the pivoted detent have been worked in with the minimum of modification to the original plan.
Baillie 1951, refers to this movement and lists a Patrick Norris, Liverpool, 1781-1829. However a more likely period is the second half of the nineteenth century.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Seconds hand broken.
- 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.1739 (Ilbert Collection)
Previous owner/ex-collection number: N37 (Ilbert Ledger)