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In 1874 Gruen filed a patent for a 'safety' pinion that prevented damage to a pocket-watch movement if the mainspring broke. In 1876 he started the Columbus Watch Manufacturing Company in Columbus, Ohio. In 1882 the company was reorganized as the Columbus Watch Company and moved to a building on Thurman Street. The company now saw itself as in the same ranks of older established American watch companies like Waltham Watch Company and Elgin National Watch Company.