Swiss silver open faced barrel less lever watch Circa 1910

Silver lever without mainspring barrel by Isaac Grasset 
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A fine and rare Swiss silver open faced lever pocket watch without mainspring barrel built to the design of Swiss Patents No. 5019 and 14528, circa 1910. Gilt brass movement, 13 jewels, the mainspring rolled around the winding shaft, straight line lever escapement, cut bi metallic compensation balance, blued steel Breguet balance spring, index regulator. Glazed gilt rimmed cuvette for viewing the movement. White enamel dial with Roman numerals, outer minute track and Arabic five minute numerals, subsidiary seconds and original gold spade hands. Engine turned case with polished borders, the back with vacant cartouche.
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Diameter: 52 mm
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Signed: Isaac Grasset Genève