English rose gold open faced pocket chronometer Circa 1805

Rose gold chronometer by Thomas Earnshaw
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An English 18 carat rose gold open faced pocket chronometer, Hallmarked London 1805. Precision movement with Earnshaw’s spring detent chronometer escapement, three armed steel balance, ‘sugar tongs’ temperature compensation, blued hairspring, florally engraved balance cock, engraved regulating scale, diamond endstone. White enamel dial with Roman numerals and rose golden hands. Plain pair cases, master’s mark IM.
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Diameter: 58 mm
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Weight: 150 g
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Signed: Thomas Earnshaw London
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Thomas Earnshaw ( born 1749, Ashton under Lyne, Lancashire, died 1829, London) first worked from 1794 to 1795 in 119 High Holborn and later also in 87 Fenchurch Street. He is undoubtedly the inventor of the spring detent chronometer escapement and prevailed his competitors inventions for a half century. Furthermore we owe to him the idea of the balance wheel made of brass and steel, which made the later compensation balance possible. In his writing ‘Longitude: An Appeal to the Public…’ he describes in detail the development of his spring detent chronometer escapement. On the side of his competitor John Arnold were such important people as Sir John Banks, president of the Royal Society, and Alexander Dalrymple, the hydrograph of the admiralty.

The watch originally comes from the important chronometer collection which was auctioned  and was sold for € 28.500,-