Following the work of John Arnold, the London watchmaker Thomas Earnshaw (1749-1829) further simplified the designs of the pocket and marine chronometers into their modern, readily reproducible form. This is a typical example of Earnshaw's marine chronometers, made from the early 1790s until his retirement in about 1820. The design is little different from the marine chronometer of the mid-20th century.

In the early 19th century (and probably from new) Earnshaw 512 was the property of the East India Company. In 1821 it is recorded as returning from India and was issued to the Company ship Thomas Grenville, Captain Manning, (in place of Earnshaw 291). Apparently it did not perform well and, on return to England, Manning was reprimanded for not informing the Committee of Shipping that it was unreliable. On inspection in 1823, Earnshaw himself stated that it “…cannot be depended upon”, and the Committee declared that they “…are highly displeased at his having so long neglected to bring the subject of the chronometers to the notice of the Committee”. This incident resulted in a new East India Company regulation concerning chronometers, in which a resolution was passed that “…the Commanders of the Company’s own ships be desired immediately at the conclusion of each voyage to report particularly on the performance of their respective chronometers”, and evidence in the Committee minutes show that this requirement was duly followed in subsequent years [FN: Arnott, Philip, ‘Chronometers on East India Company Ships 1800 to 1833’, Antiquarian Horology, Vol.30 No.4 Dec.2007].

The subsequent history of the chronometer is unknown until its purchase by Sir James Caird Bt., from the London horological dealers Clowes and Jauncey for £16 in July 1936. The chronometer has been on display at the NMM virtually constantly since the mid twentieth century. It was loaned to an exhibition in Pusan City Museum, Korea between April and June 1997, and to La Corderie Royale, Rochefort, France between October 1997 and January 1998.