American gilt Trade Union railroad lever watch Circa 1910-1920

Trade Union railroad watch by Hamilton Watch Co.
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A rare American Trade Union railroad watch. Ball Watch Co. model Grade 999 Brotherhood of Locomotive Engineers Official Standard by Ball Watch Co., circa 1910-1920. 17 Jewel movement, concentric damascened full plate, jewels in settings, bimetallic balance, overcoiled spring, swan’s neck regulator, stem wound, lever set. White enamel dial, black Arabic numerals, subsidiary seconds and blued hands. Plain open face case by Keystone Watch Co., Silveroid, Ball Model.
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Diameter: 54 mm
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Signed: Trade Mark B of L E Standard Ball & Co., Cleveland – Official B of L E  Standard Ball & Co. Cleveland