English silver pocket chronometer of high quality Circa 1807

Open faced pocket watch with spring detent escapement
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An English pocket chronometer of high quality with spring detent escapement according to John Arnold and Arnold’s Z balance, circa 1807.
Silver case with case maker’s punch mark “TH” (Thomas Hardy). White enamel dial -signed “Arnold 2027“-, with Roman numerals and a subsidiary dial for the constant seconds. The movement -signed “JR Arnold London Inv.t et Fecit – is a full plate movement with a chain/fusee, a z-shaped bimetallic chronometer balance with 4 screws and 2 movable weights and a freesprung blued helical balance spring.
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Diameter: 57 mm
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Weight: 172 g
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Signed: John Roger Arnold, London, Inv.t et Fecit
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John Roger Arnold (1769-1843) was the son of renowned British horologist John Arnold. He began his apprenticeship with A.-L. Breguet in Paris in 1792. The younger Arnold became a member of the Clockmaker’s Company in 1796 and was a Master in 1817. He took up a partnership with E.J. Dent in 1830 and the two craftsmen experimented heavily during their work together; in particular they concentrated on the effects of magnetism on chronometers. Dent left Arnold in 1840, whereupon Arnold continued working on his own but died only three years later. Charles Frodsham bought the business after Arnold’s death in February 1843 and it flourished until 1858 under the name Arnold and Frodsham.