German silver open faced cylinder pocket watch Circa 1800

Silver cylinder watch by Christoph Matthäus Hahn
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A South German silver open faced cylinder pocket watch, circa 1800. Full plate movement, one barrel, key wind, cylinder escapement, five arm brass balance. White enamel dial with Arabic hours and outer minute divisions. Plain case.
Case numbered, movement signed.
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Diameter: 55 mm
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Weight: 116 g
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Signed: Hahn Hofmechanicus in Stuttgart
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Christoph Matthäus Hahn was born on April 15th, 1767, in the region of Stuttgart. He was the son of Philipp Matthäus Hahn and worked in his father’s workshop at first and then together with his brother Christian Gottfried Hahn. The brothers were Hofmechanici (court mechanics) in Stuttgart. Christoph is best known for his calculator machines which he made together with his father and later, after his father’s death, on his own. The Hahn’s calculating machines are considered the predecessors of modern computers and the name Hahn is found in every book about the history of computers. Besides making early computers, Christoph (as well as his father) produced a few calendar clocks and watches. Only a few are known to have survived. One in The British Museum and one in the museum of La Chaux-de-Fonds, Switzerland. Another was owned by the former Time Museum in Rockford, USA. In 1790 Christoph was awarded the title of Court Mechanician in Stuttgart. He died in Stuttgart on June 1st, 1833. After his death, August Bacher took over Christoph Hahn’s workshop.
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Philipp Matthäus Hahn was born on November 25^th, 1739 in Scharnhausen and he died on May 2^nd, 1790 in Echterdingen. He was a German pastor, astronomer and inventor. In about 1763 he devised a precision sundial or helio chronometer that incorporated the correction for the equation of time. In 1774 he further designed one of the earliest mechanical calculators. Hahn was also a renowned clockmaker, several horological museums display his works.