English watch with regulator dial and chronoscope Circa 1871

Unusual gold open faced pocket watch by Dent 
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An unusual English precision pocket watch with regulator dial and chronoscope, circa 1871.
18 Carat gold, polished, tiered case, gold dome, and chronograph pusher via pendant. Signed enamel dial with radial Roman numerals on an eccentric chapter ring, auxiliary seconds, centre chronograph hand, and blued hands. Signed, numbered, chatoned, frosted, gilt 4/5 plate movement with Nielsen calibre, Patent, English lever escapement, and screw compensation balance.
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Diameter: 50 mm
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Weight: 125 g
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Signed: Dent, 33 Cockspur Street, London
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Definition of chronoscope: an instrument for the precise measurement of small-time intervals (as by means of a falling rod, released pendulum, or an electronic device)