French silver chronometer constructed in England Circa 1879

Silver open faced pocket chronometer by Bernard Poitevin
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A very unusual and especially heavy French silver open faced pocket chronometer, Hallmarked London 1879. Very fine chronometer movement in the manner of Earnshaw, spring detent escapement, unusual helical hairspring, probably made of palladium. White enamel dial with Roman numerals and gold hands. Plain case.  in English construction,  Case and movement with matching number, case with additional number, cuvette signed and numbered, dial signed.
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Diameter: 61 mm
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Weight: 227 g
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Signed: Poitevin. Paris
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This chronometer is very interesting because it is signed by an important French chronometer maker in Paris, but the construction is completely English and the case has London hallmarks as well. It can therefore be assumed that the chronometer was made in England on behalf of Poitevin. Bernard Poitevin worked as a Parisian watch and chronometer maker between 1850 and 1900. He founded the company B. Poitevin & V. Lejeune. His shop was located in Rue Richelieu (1850) and Rue Vivienne 22 (1860-1900). Poitevin supplied quality watches, watches with complications, such as watches with striking mechanism, chronographs and 1st class chronometers with bulletin from the Geneva Observatory.