3/8" and 11mm dovetails are common on rimfire rifles. We manufacture picatinny mounts for the CZ 452, 453, 455, 511, and 512. CZ made guns with 3/8" and 11mm dovetail receivers. One of the most commonly asked questions we receive is "How do I know which dovetail I have?". The easiest way to figure out which dovetail your gun has, is to measure the top of the dovetail from point to point.
.50" = 3/8" American dovetail
.43" = 11mm European dovetail