In my opinion
.... It seems like a whole lot of trouble for 4 little digits. If it is a Romanian piston, leave it be, it's an actual original part, be thankful it doesn't say Tapco. If 4 serial digits bothers one that much, how is sticking a still mismatching Chinese, Yugoslavian, Russian or Albanian gas piston going to make it match, then that part is technically not original Romanian like the one in it. In my book, knowing the Romanians marked their pistons, I would still deem it a mismatched rifle even with a numberless piston.
It''s a Romanian, 98% of the time they don't match, it's the nature of the beast. But, hey, what do I know, I will bet it works just fine as is, my 3 mismatched ones work as well as the matching one
Take a brillo pad and scrub them offending numbers off.
Congrats on a nice purchase
and welcome...