Rare George III silver pair cased pocket chronometer by French, Royal Exchange, London, London 1810, signed fusee movement, no. 226, with spring detent escapement, engraved balance cock with mask, diamond endstone, free sprung helical hairspring, 'sugar-tong' compensation, flat steel three arm balance and cylindrical pillars, signed and numbered dial with Roman numerals, minute track and subsidiary seconds, gilt disc hands, within plain matching cases, case maker 'DW' (Daniel Willmott), 47mm; key - ** The 'sugar-tong compensation', an invention of Thomas Earnshaw, is an arrangement with two bimetallic arms with one pin on each end. Instead of sliding along the balance-spring the gap between the two pins widened in cold weather and closed in hot, which has the same effect. Owing to its appearance and action, Earnshaw’s curb is usually known as a 'sugar-tong compensation'. It is thought that these watches were made to withstand robust use rather than watches with the heavier bimetallic balances that could easily break the balance pivots if subjected to shock. This invention must date from circa 1795. Ask a Question Sell One Like This

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