One-day marine chronometer, fusee with Harrison’s maintaining power and an Earnshaw-type spring detent escapement. The earliest record for Arnold No.494 shows it belonged to the Admiralty and was issued for use on board HMS Forte, which sailed for Jamaica in April 1821. It spent time in Halifax, Havannah, and Barbadoes, before returning to Portsmouth in September 1824. Between November 1827 and July 1830, the instrument was issued for use on board HMS Columbine, again operating in the Atlantic between Havannah and Bermuda. The chronometer was taken in exchange for new chronometers by E.J. Dent in January 1851. It look part in a television documentary titled Longitude Zero, on Tuesday 9 August 1960.