Due to the stenciling, style of block lettering, the way the can is sealed and style of box I would confidently bet that it is Yugoslavian made 8mm ammo made for contract. Look up Yugoslav M67 or Yugoslav M75 sealed crates to see what I’m talking about.
OP it's your box so you can do what you want with it but I'd leave it sealed personally until you can find more info on it. Maybe some Yugoslavian historian buff may pay a lot of money for it who knows.