Silver:

There are at least 3 different variations where the rim diameter is different. Mauser began with a cartridge in the early 1890s with a larger cartridge in the M93 series, than it's parent 8mm version, the M88. Then there's the Chinese variant called something like 7.4X57. Then either it was standarized in the 1930s or another variant referred to as 7X57R.

Kind Regards,

Raimey
rse