I've seen two types of ink stamps on the Code 25 mags:dyi said:


The Code 21 mags may have a round proof mark on the lower right side:

I've never seen any type of ink stamps on the Arsenal (Code 10) mags.
Not that I can figure out! The Bulgarians don't seem to have been nearly as liberal or varied with their stamping as the Russians. The ink they used wears away pretty easily; I've received many new-condition Code 21 and 25 mags that didn't have any proof marks... not sure if they wore off during storage and transit, or if they never had 'em to begin with.