This is 303 british, but it isn't standard mk7. This ammo, designated as Mk 8z, is designed specifically for machine guns, has a 174/5 grain boat tail bullet with a very high ballistic coefficient, and is loaded with nitrocellulose powder, as opposed to cordite.
It is of Belgian manufacture, 1948 vintage. Some rounds have minor corrosion and blackening, but it is surface discoloration only. None of these should be too badly corroded to fire. Being so old, it has minor hangfires that are barely noticeable, which is pretty typical of ammo this age, but of the 40 or so rounds I fired (before I found out what it specifically was,) I had zero fail to fires or significant hangfires.
I am unsure on the price, but it wont be cheap. All 250 ish rounds of ammo are in 50 round bandoliers, all of it on stripper clips. Normal 303 brit on clips runs at least 70 cents a round, but seeing as this is some specialty stuff, it will probably be quite a bit more.
No lowballs please, and I will answer any questions you have.