c.1887 Keystone Watch Co. Patent "Dust Proof" Watch: Movement c.1887 Keystone Watch Co. Patent "Dust Proof" Watch - 18-Size, Gilt-Damaskeened Plates, 10 Jewels, ETP ~7,400. In addition to Abraham Bitner's Patent Micrometric Regulator, this watch features many other patents issued to Bitner during his leadership...