Hi,
Chris , the eng. No. is not the real CZ stamps , never ever been stamped on the right side , no biggy though, When you want to split the cases , Iv'e got a set case splitters/pullers to lend .
Check to see if they are matching cases, stamped on each half under the crank, outside , three digits , dont bother trying to build an unmatched set of cases until they are checked, by an engineer to guarantee they have "line bored"
Iv'e got an old spare parts book (FREE) , No you don't have to get a TATOO to belong to the brotherhood .
Cheers