English 18 Carat yellow gold chronometer pocket watch Circa 1807

Gold open faced pocket watch 
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A very fine and extremely rare English, 18 Carat yellow gold chronometer with Earnshaw’s spring detent escapement and patent bimetallic sugar tong compensation, circa 1807. Sugar Tong pocket chronometer by Thomas Mc Cabe, Royal Exchange, London, movement by Thomas Earnshaw. The case is made by James Richards with London Hallmarks for 1807-1808. White enamel dial with radial Roman numerals and outer minute divisions, subsidiary seconds. Gold Breguet hands.
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A gilt brass full plate movement with ring turned pillars, fusee and chain, Harrison’s maintaining power, Earnshaw’s spring detent escapement, escape wheel with end stones in screwed Chaton, large polished steel flat rim three arm balance with diamond end stone, flat blued steel balance spring, chased and engraved single footed balance cock, Earnshaw’s bi metallic sugar tong compensation coupled with the index regulator.
Dial and movement signed.
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Diameter: 55,5 mm
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Signed: James Mc Cabe  London
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The Sugar Tong compensation. Although Earnshaw made pocket watches with bi metallic balances and free sprung helical springs, he equally often turned them out with an uncut flat steel balance, spiral spring, regulator and compensation curb. This arrangement has two arms with a pin on each end, instead of sliding along the balance spring the gap between the two pins widened in cold weather and narrowed in hot, which has the same effect. Owing to the pincer like appearance and action, this curb is commonly known as a sugar tong compensation. It is thought that these watches were for clients who needed a watch that could withstand robust use rather than watches with the heavier bi metallic balances that could easily break the balance pivots if subjected to shock.