I don't know how you are going to get the disc attached to the shaft of an assembled shock, but here goes:
the disc is slightly cupped; diameter of the installed cupped disc is 1 5/8";
the disc thickness is approximately 1/16";
the 4 holes in the disc are 1/4" diameter, oriented at 12, 3, 6, 9 o'clock.
each disc has a tiny nick, or notch, in a tiny dent on the edge.