Plate glass, 31.125 in. O/a lg, 31.0625 in. O/a w, 0.125 in. Thk, 14 concetric circles spaced 2 in. Apart, one circle 29.200 in. Dia, 24 radial lines spaced 15 degree intervals, radial and circle lines etched or ground 0.009 in. Wide and 0.005 in. Deep, 2 holes 0.250 in. Diameter on 23.125 in. C to c, 10 slots on one side 0.187 in. W and 0.250 in. O/a deep
