Swiss gold pocket watch with constant force escapement Circa 1860

Gold keyless and key-wound pocket watch attributed to Louis Richard
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A fine and extremely rare Swiss 18 carat gold open faced keyless and key-wound pocket watch with highly unusual experimental constant force escapement, circa 1860. Matte gilt movement, gold train, wolf’s tooth winding without coasting, escapement which combines detent chronometer and lever with constant force action: the escape wheel consisting of two stacked wheels of different diameter, the lower delivering the impulse, the upper for locking with a detent spring, impulse is delivered to a roller mounted in jewels on a pivoted detent, the roller turns freely to minimize the friction, the locking spring is part of the detent mounted perpendicular to it, detent with spiral spring acting as a remontoir, end of the detent fitted with a large roller mounted in jewels rolling on a large half-cylinder mounted on the balance staff, the energy in the constant force spring giving impulse to the balance via the roller, constant force spring mounted on an adjustable plate to control the energy delivered to the balance and acting as an amplitude adjustment, cut bimetallic compensation balance with gold meantime and temperature adjustment screws, flat balance spring, index regulator with micrometric screw. Gold engine-turned cuvette. White enamel dial with Roman numerals, outer minute track, subsidiary seconds and original blued steel spade hands. Polished case, master mark FS, the back cover engine-turned. Stamped FS inside back cover, movement scratch numbered on the dial plate, case numbered.
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Diameter: 49.5 mm
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Signed: No name