28ga = .550"
32ga = .526"
36ga = .506"
67.49ga = .410"
12mm =.472"
A .410 is a .410 regardless of whether some maker stamps 12mm or 36ga upon it. 12mm is approximate size of the chamber & 36ga is just a smaller number than 32. If it's made in a proof law country look to the proofer's bore stamp, it will be different than the makers if either of those marks are used.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra