This was once used on the old telephone circuit of the Gaston Shoals- Spartenburg SC transmission line (cir 1906-08). These are the only early gray glazed glaze-weld unipart pin types I have ever seen.... The pin was custom made to conform to the angle of the tower legs where the pin mounted so that the insulator was held vertical, The pins were likely custom made by the Airmotor Co to fit their towers. These gray glazeweld pieces were used for many miles of line for the high line talk circuits but only four have been found unbroken as the lineman smashed them off the towers when they removed the copper wirereason, the Elton Gish confirmed it is a U-927d