Steel, qq-s-634, comp1010 through 1025, cadmium plate, qq-p-416, type 2, class 1, 3.000 in. Dia, 1.500 in. Depth, three 3/8-16 unc2b0.300 in. Deep thd holes unequally spaced on a 2.312 in. Bolt circledia, reference cross 3/16 by 3/16 scribed in the exact center ofreceptacle