Plate, steel per mil-s-5636 or mil-s-6049 or mil-s-18720, cadmium plate per qq-p-416, type 1, cl 2, 2.500 in. Lg by1.781 in. Wd by 0.156 in. Thk, heat treatment per mil-h-6875, rockwell c38 to c42; spring, steel music wire per qq-w-470, 0.045 in. Diameter by 2.172 in. Lg approx