back in the mid-1980’s a lot of this ammunition showed up in the US at gun shows. Ball, orange tipped tracer and black tipped AP were pretty common. All had brass cases and were headstamped “ZV 69”. I think that if you look closely, you will see that the primer is blackened, chemically, not lacquer, AND has a black primer seal. Fast forward to the Gulf War in 1991. I found a FN-FAL 20 rd. magazine in the desert of Kuwait filled with this exact same ammunition! As for the blackened primer, this seems to be typical of Czech military ammunition, regardless of wether it is corrosive or non-corrosive primed. The ZV factory code is usually seen on brass cases, but occasionally on steel as well. I’ve been told it is an export headstamp, and also that it is a specific factory, seperate from “bxn” and “aym”. It seems odd to only have a factory making export ammunition though.