Heavy gold English watch with rack lever escapement Circa 1806

Gold pair cased rack lever pocket watch 
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A heavy English gold pair cased pocket watch with rack lever escapement, according to the patent of Peter Litherland (1756-1805), circa 1806. English gilt full plate movement with rack lever escapement signed Liverpool, engraved balance cock with diamond endstone, key wind, chain/fusee, three-arm polished steel balance, engraved indicator scale with polished steel indicator.
18 Carat gold polished outer case and 18K gold polished inner case with hallmarks 1806 and casemaker’s punch SB.
White enamel dial with Roman hours, subsidiary dial at six o’clock, pink gold spade hands.
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Diameter: 57 mm
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Weight: 155 g
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Signed: No name
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Peter Litherland was a watchmaker and inventor. He was born in Warrington and later moved to Liverpool, which was then the centre of the watchmaking trade. In 1791 he patented the rack lever escapement for watches, which was more accurate than the commonly used verge escapement. One of his watches is in display in the World Museum Liverpool.
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Reference 0025000