This is a metal encased composition cable insulator with articulating cable clamps/guides I picked up recently. The base diameter is 3.925 inches and the height is 5.25 inches. It accepts a 1 inch threaded pin. On the front is embossed PTD NOV 16 1897; the rear is embossed with the numerals 211 (upside down). The only insulator patent issued that day was #593,689 to Louis F. Rembe of Haverstraw, NY., for a self-tying design. Any additional info on this insulator's history and use would be greatly appreciated. A bottom view is located at [247941624] UPDATE:The difficult to read embossing is actually PTD MCH 16 1897 and was issued to Luscomb (Johns-Pratt Co.), not Louis Rembe as I initially reported. See Jim Colburn's posting [id=249816172]