A most interesting fast beating pocket chronometer, circa 1815.
Substantial but later purpose made engine-turned silver hunter case hallmarked London 1888, casemaker GJT (George James Thickbroom, Spencer St, Clerkenwell). Unusual fullplate going-barrel movement with cap jewels on balance (diamond) and escape, with tall mainspring barrel held under a barrel-bridge. John Arnold's spring-detent detached escapement, the replacement detent mounted within a slot in the top plate and working in compression and banking against an adjustable gold disc. Arnold’s two-arm 'Z' compensation balance, the 7-turn blued-steel helical balance-spring with Arnold's terminal curves. Original one-piece signed enamel dial, blued-steel hands dating from the time of re-casing. 58 mm diameter, 19.5 mm deep.
John Roger Arnold, the famous son of a famous father, a very good watch and chronometer maker in his own right, apprenticed to and retaining strong connections with the Breguet workshop, this rare caliper in particular showing Breguet's influence.
NB: This movement has a faster beat that normal with six vibrations in two seconds rather than the usual four or five. This needs rather more power to run and thus the taller mainspring barrel making the best use of space. Retaining his fathers patented detent, compensation balance and terminal curves, this watch will no doubt have been one of the best timekeepers of its day, and all within a slimmer than normal case that would have been perfect for civilian use.
The well made replacement case in fine condition, having a split two-piece push operating both the sprung front and rear covers. The original dial with some lights hair cracks and the movement showing some signs of wear and tear, but nothing serious. The detent is a replacement probably dating from the time it was put into its present case, but is possibly more modern. A good example of John Roger's best work that has been re-cased, and priced accordingly. Serviced and guaranteed.
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