Important English high quality marine chronometer Circa 1791

Important museum quality chronometer
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An important numbered museum quality marine chronometer, made by John Arnold & Son in London, England, circa 1791. The open faced plain case is fitted in to a very high quality eight cornered wooden box which is true to the original but later made. The original dial has black Arabic minute and Roman hour numerals, a subsidiary seconds dial with Arabic numerals at six o’clock and blued steel hands. The Arnold spring detent chronometer movement has a helical hairspring.
Dial and movement have matching numbers and are signed.
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Diameter:  16.5 cm
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Signed: John Arnold & Son, London
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According to the Staeger list only six earlier John Arnold & Son marine chronometers in this version are known. The watch was part of one of the most important European chronometer collections. Almost all Arnold marine chronometers from this period are in important museums and collections. No.63 is in the Science Museum in London, No. 12 in the British Museum. They are very rarely offered at auctions. No.85 was part of an auction in 2017 and sold for € 55.800.
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John Arnold

John Arnold was born in 1736 and died on August 11th, 1799. He was an English watchmaker and inventor. Arnold was apprenticed to his father, who was also a clockmaker in Bodmin, Cornwell and probably also worked with his uncle, a gunsmith. Around 1755, at the age of 19, he left England and worked as a watchmaker in the Hague, Holland, returning to England around 1757. In 1762, he met William McGuire on whom he made a sufficient impression and McGuire gave him a loan, enabling him to set up a workshop at Devereux Court, Strand, London. By the time he was 28, Arnold’s watches, be they verge or cylinder, displayed interesting original components such as straight line compensation curbs and minute repeating by increments of 10 minutes instead of the more common 15 minutes. In 1764, Arnold obtained permission to present an exceptionally small half quarter repeating watch with a cylinder escapement mounted in a ring to King George III. He made another watch for the King around 1768, which was a gold and enamel pair-cased watch with a movement that had every refinement, including minute repetition and center seconds. It was around 1770 that Arnold developed a portable precision timekeeper. His basic design was simple whilst consistently accurate and mechanically reliable. Importantly, the relatively simple and conventional design of his movement facilitated its production in quantity at a reasonable price whilst also enabling easier maintenance and adjustment. He successfully found a way to simplify Harrison’s timekeeper design. He established himself at 2 Adam Street, Adelphi Buildings, Strand, in 1771 and researched marine chronometers here over the next eleven years. Arnold was the first to design a watch that was both practical and accurate, and also brought the chronometer into use in its modern sense, as a precision timekeeper. His technical progress enabled the quantity production of marine chronometers for use on board ships from around 1782. Arnold was admitted to the Clockmakers’ Company in 1783. The important French watchmaker Abraham-Louis Breguet was a very good friend of Arnold. It appears Arnold gave Breguet permission to incorporate or develop any of Arnold’s inventions and techniques into his watches. Arnold’s son John Roger Arnold was born in 1769 and served an apprenticeship with both his father and Abraham-Louis Breguet. In 1787, he and his father founded the company, Arnold & Son. John Arnold also appears to have been the first to think of the concept of the tourbillon. He seems to have experimented with his idea but died in 1799 before he could develop it further. It is known that Breguet made a successful and practical tourbillon mechanism around 1795 but he acknowledged Arnold as the inventor by presenting his first tourbillon in 1808 to Arnold’s son, John Roger, as a tribute to his friend Arnold Sr.