I’ve just rebuilt the caliper on my ’95 ETZ251, Kanuni built bike. It has ‘MZ’ cast into the outside and Grimeca cast into the inner surface of the caliper, not visible until it’s off the bike. The safest way I found to identify the manufacturer was to accurately check the diameter of the pistons – the MZ Shop gives details of the piston diameter of each type, so you can be confident of ordering the correct parts.
Drew M