Early French silver antimagnetic lever chronograph Circa 1910

Silver antimagnetic chronograph with register by Leroy
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A very fine, extremely rare and very early French silver open faced antimagnetic chronograph keyless lever pocket watch with instantaneous 30-minute register, circa 1910. Frosted gilt movement, 21 jewels, straight-line lever escapement, cut-bimetallic compensation balance, blued steel Breguet balance spring, index regulator. Paramagnetic snap-on cuvette probably made of tantalum. White enamel dial with Roman numerals, outer minute divisions, outermost fifths of a second chronograph divisions, subsidiary 30-minute register at 12 o’clock, subsidiary seconds at 6 o’clock and original blued steel spade hands. Polished case, button for start/stop and return-to-zero of the chronograph in the crown, soft iron band surrounding the movement. Dial and cuvette signed, case numbered.
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Diameter: 52 mm
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Signed: Leroy Paris