The Louis Fort patent bracket and insulator for use street light wiring. The cast iron bracket is embossed on one side of the arm: LF MFG CO / JERSEY CITY / N J On the other side of the arm is embossed:PAT 9.18.17 / AND PAT'S / PENGING The clamp portion of the bracket is embossed D at front and back. Each of the two halves of the insulator is embossed below the clamp groove:"D" / PAT SEPT 18.1917 The diameter of the insulator is 3 inches and the height is 3 7/8 inches. The length of the arm is 3 1/2 inches from the insulator to the base plate. The lag screw portion is 5/8 inches in diameter and has a length of 2 1/2 inches. Reference: http://reference.insulators.info/patents/detail/?patent=1240330&type=U