Unusual Swiss 18K gold split-seconds chronograph Circa 1860

Gold hunting cased lever pocket watch 
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A very fine Swiss early and unusual 18K gold hunting cased two-train independent split-seconds chronograph keyless lever pocket watch without return to zero function and with 1/4th second diablotine, circa 1860. Engine-turned case with polished borders and band. Hinged gold cuvette with engine-turned border. White enamel dial, radial Roman numerals, outer minute track and outermost fourths of a second ring, subsidiary 1/4th second foudroyante, blued steel Breguet hands. A rhodium-plated, two-train special calibre with tandem winding, 30 jewels, Geneva striping decoration, counterpoised straight-line lever escapement, cut bimetallic compensation balance, blued steel Breguet balance spring, index regulator, independent split-seconds chronograph with push-pieces in the bezel for stop/start and stop/rejoin.
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Diameter: 57 mm
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Signed: P.H. Doret Le Locle
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This watch can be considered a true chronograph with an independent train. It is interesting because it probably dates from before the Adolphe Nicole patent of 1862 and is, therefore, one of the early developments of the split-seconds mechanism for chronographs. Unlike the Adolphe Nicole patent, the hands of the present watch cannot be reset to zero.
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The feature known as a diablotine is a small subsidiary dial on a chronograph or independent centre seconds pocket watch, the hand of which moves in a jumping manner at intervals of 1/4 or 1/5th of a second. The term literally means ‘little devil’. The diablotine is halted when the chronograph or centre seconds is stopped and the fractions of a second can be read.