The T-65 designation indicates that IT IS "7,62 x 51 cartridge cases.
The “ZV” is either Zavod Vlasim (Vlasim Factory) or “Zbrojovka Vlasim”( Vlasim Arsenal). This was the Head stamp used on Ammunition made by Sellier & Bellot Vlasim ( as a CSSR “Narodny Podnik” (People’s enterprise).) for all export ammunition (Usually through “Omnipol”, a Prague-based CSSR “exporter” of all sorts of products, from Tractors to Machine tools to Ordnance.)
ZV is found on 7,62 x51 (Not Nato, as it does not meet the “Nato Standard” in that the primers are corrosive), on 7,62x54R, on 7,62x45 Czech, and other calibres in common use in the “non-aligned” countries during the cold war…A lot of “ZV 69 and 70” ammo came out of Mellilla (a Spanish Enclave in North Africa (Morocco)…whether it was captured by the Spanish Foreign legion in operations against local Saharian Rebels, or actually bought by Spain is unknown. Other Arab states would have acquired it as well in the 1960s to 70s.
ZV was the “Export” headstamp, bxn was the Warsaw Pact headstamp for S&B.
It started to come into the Milsurp Market in the Mid 1980s, when quantities of “1980s” S&B made 7,62x51 ( Packets Marked .308) came onto the market as well ( h/s : 80 o 308 o ). The crates and cans were exactly the same as the ZV ones.
BTW, the design of the Czech Ammunition crate has remained the same since the 1920s ( when used to pack 7,9mm) through the Communist Period ( various 7,62s) to today (5,56 and 7,62Nato).
ZV marked ammo is “iffy”, with many FTF due to primerer issues…I have seen crates where the wood suffered from “dry rot” (after water immersion), so Bad storage in North Africa or wherever
may be the cause.
The ammo is good for Plinking (when it fires) and otherwise for Bullet and Powder…the Berdan cases can be reloaded ( .217"primer is not crimped) if one is of a mind to. Decapping Iffy Primers required a good Hydraulic set up…they might not go off with a Firing Pin, but a chisel may certainly set them off.