Firstly, "ZV" is Zbrojovka Vlasim, the export mark for Military ammo of Sellier & Bellot, of Vlasim, Czechoslovakia (Then) and NOT "Brno" which had a headstamp "Z" in the 1930s and 40s, for their acquired Factory in Bratislava ( and leater durng WW II, set up at Povaske Strojarne (in Slovakia), which became the "PS" factory of sporting ammo after WW II.



The original factory, before acquisition by ZB ( 1935-6) was "Circle M", and before that "JR" ( Jiri Roth...connected to Georg Roth of Vienna ( pre-WW I).



The Blackened primer is found on 1969 dated 7,62x51 ( Labelled "T-65", the US trials designation which became the 7,62 Nato cartridge.). Reason for the Chemical Blackening is unknown, whether to identify Primer composition, or special order, or maker of the primer (S&B makes most of its own, at a separate factory from the Ammo Plant at Vlasim, but primers in the CSSR were also made by other factories as well. Thye Black primer had been used on previous "ZV" 7,62x39 and 54R as well ( export)



ZV 70 have normal brass primer cups.



BTW, the Czech word "Zbrojovka" means "Arsenal or Armoury" in English, and can refer to any sort of Ordnance Plant; not just rifles or ammunition.



As most surplus ZV69 and 70 came from Spanish Enclaves in North Africa(Melilla, Teruen, etc) the primers are a bit Iffy, especially the Black ones (69). so beware if shooting it.