Does anyone know how old the Romanian/Eastern European steel mags that we commonly see are?

Not really a good way to tell, the one distinction being the last rib closest to the spine and whether it continues up into the feedlip sideplate (1st gen euro) or makes a turn towards the spine (the "hockey-stick" , 2nd gen euro).  Many are from the 1950's so they are 50+ years old now, Russian slabsides were only made from 1948-1953 so they are all a minimum of 62 years old. Some former combloc countries still make metal mags so could be very recent.