Thomas Earnshaw, A historically interesting pocket chronometer with Wright's patent punchmark in later silver pair case, circa 1783

finely engraved gilt full plate movement with punchmark for Wright's Patent, Earnshaw's spring detent escapement, pierced and engraved masked balance cock, large diamond endstone, gilt-brass three armed balance, turned pillars, gilt-metal movement cover, white enamel dial, reverse signed Weston, roman numerals, subsidiary seconds, gold hour and minute hands, later plain silver inner and outer cases, dial and movement signed Jessop, Southampton Street, London, dust cover further signed Jessop, London, case stamped with maker's mark DW, case hallmarked, London 1805, accompanied by a copy of Randall, The Time Museum Catalogue of Marine Chronometers.

Time Museum Inventory No. 4127

Randall, cat. no. 52

Thomas Earnshaw was one of England's most famous chronometer makers. He was born in 1749 in Lancashire and was apprenticed at the age of fourteen. He was the inventor of the spring detent escapement as well as the compensation balance. He submitted seven chronometers to the Board of Longitude from 1791 to 1798 and in 1805 received a portion of the Longitude Prize. His prize amount of £3,000 was part of the remaining £10,000 available, divided between John Arnold and Thomas Mudge. Earnshaw was not pleased with the division and lodged a protest with the Board called "Longitude: An Appeal to the Public", describing the development of his escapement. Apparently the Board did not change their finding. He died in 1829.

The present watch represents both the earliest Earnshaw chronometer in the Time Museum Collection and the earliest known in existence created during the heated contest and race for recognition of the invention of the spring detent escapement between Earnshaw and John Arnold. 

The movement of the watch bears the punchmark for Wright's patent.  When Thomas Earnshaw invented his famed form of spring detent escapement he could not afford the application fee to the patent's office.  In February of 1783, patent no. 1354 was taken out by Thomas Wright, watchmaker to the King, who agreed to patronize Earnshaw and pay the 100 guineas in return for a percentage of the profits of the selling of Earnshaw's watches to retailers.  The specific punchmark on the movement of this watch remains unique.  By 1784, it is likely that Earnshaw had repaid the dept of 100 guineas as after that time watches made with his escapement no longer bear Wright's punchmark on the movement.

Furthermore, Earnshaw's early watches with spring detent escapements were also signed on the dials by the various retailers, or 'makers' as they were referred to by Earnshaw.  This explains the appearance of the signature for Jessop on the movement, dust cover and dial.