Rare Swiss gold split-second keyless pocket watch Circa 1870

Gold hunting cased lever chronograph
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A very fine, rare, early and unusual Swiss 18K gold hunting cased two-train independent split-seconds chronograph keyless lever pocket watch with 1/4th second diablotine, circa 1870. Engine- turned and polished case with a reeded band, the interior of the front cover with engraved dedication. Hinged gold cuvette with engine-turned border, glazed gold-rimmed cover to view the movement.

White enamel dial, three-piece, radial Roman numerals, outer minute track and fifths of a second ring with Arabic numerals 20-240, subsidiary 1/4th seconds, blued steel Breguet hands. Nickel-plated movement, double 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 band.
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Diameter: 57 mm
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Signed: L.C. Grandjean Locle
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Unlike watches with the usual independent seconds’ mechanism, this watch can be considered a true chronograph with an independent train, because the chronograph hands can be reset to zero. It can therefore be regarded as one of the first applications of the Adolphe Nicole patent front 1862 and one of the first developments of the split-seconds mechanism for chronographs.
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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.