English technical interesting pocket chronometer Circa 1812

Open faced gold pocket watch by John Barwise
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A beautiful English pocket watch chronometer, with Pennigton chronometer balance, circa 1812.
18 Carat gold case with London hallmarks 1812, casemaker’s punch IM and matching numbers on case and movement; Earnshaw spring detent escapement equipped with Pennington’s ‘Double L’ chronometer balance, diamond end stone, cylindrical hairspring, screwed gold chatons and the main plate signed and numbered; white enamel dial with Roman hours, sunk subsidiary dial for the constant seconds, gold hands and also signed and numbered.
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Diameter: 53mm
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Weight: 157 g
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Signed: Barwise London
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John Barwise was one of the leading watchmakers in London and one of only a few watchmakers to serve as a judge on the “Board of Longitude” comparison of John Arnold and Thomas Earnshaw’s chronometer.