Matl aluminum alloy, 2024-t4; finish chemical film, mil-c-5541, class 1a; machine finish 63.0 microinches all over; 1.650 in. O/a lg; 1.380 in. O/a w; aperture size 1.180 in. Lg, 0.880 in. W; two 2-56unc-2b holes irregularly spaced; two 4-40unc-2b holes irregularly spaced