French 18k yellow gold antimagnetic pocket watch Circa 1910

Gold keyless winding lever with chronograph 
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A very fine and extremely rare French, very early antimagnetic, 18k yellow gold, keyless pocket watch, circa 1910. With chronograph and instantaneous 30-minute register. The case with a monogram and an inside dedication inscription, a button for start/stop and return-to-zero of the chronograph in the crown, soft iron band surrounding the movement. A paramagnetic snap-on cuvette is probably made of tantalum.
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White enamel dial, Arabic numerals, outer minute divisions, outermost fifths of a second chronograph division, subsidiary 30-minute register at 12 o’clock, subsidiary seconds at 6 o’clock. Blued steel spade hands. A frosted gilt movement, 21 jewels, straight-line lever escapement, cut bimetallic compensation balance, blued steel Breguet balance spring, index regulator. Dial and cuvette signed.
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Thickness: 18 mm
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Diameter: 54 mm
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Signed: Leroy  Paris
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The case is slightly scratched, and the dial is chipped.