Interesting that the size for a silver $25 can be smaller than a base metal token.

12.050 Specifications for tokens.
1. Unless the chairman approves otherwise, tokens must be disk-shaped and must measure
as follows:
(a) No token may be smaller than 1.459 inches or larger than 1.95 inches in diameter, and no
token may be from 1.475 through 1.525 inches in diameter;
(b) One dollar denomination tokens must be from 1.459 through 1.474 inches in diameter, from
.095 through .115 inch thick, and, if the token has reeds or serrations on its edges, the number or
reeds or serrations must not exceed 150;
(c) Five dollar denomination tokens must be 1.75 inches in diameter, from .115 through .135
inch thick, and, if the token has reeds or serrations on its edges, the number of reeds or
serrations must not exceed 175;
(d) Twenty-five dollar denomination tokens must be larger than 1.75 inches but no larger than
1.95 inches in diameter (except that such tokens may be 1.654 inches (42 millimeters) in
diameter if made of 99.9 percent pure silver), must be .10 inch thick, and, if the token has reeds
or serrations on its edges, the number of reeds or serrations must not exceed 200; and
(e) Tokens of other denominations must have such measurements and edge reeds or
serrations as the chairman may approve or require.
2. The chairman shall not approve any tokens of denominations lower than one dollar.

This also explains why you never see any Nevada 50c tokens, like those minted in the 1960's, which were half-dollar size.