Yes, it is steel core, made t the Santa Barbara plant in Spain, box you have is dated 1982 production (of course) As I remember, it was good shooting ammo. but it does have a steel core. like the M855, 62 grain. Also, if I remember, in the good old days around 2000-2001..lol.. You could get 1000 rounds of that for $95-100.
As far as I know, the only way to buy it today is to run onto it just like you did. It's been sold out at the importers for years.
as far as the ap, it is just the same as the green tip stuff that the US and nato makes. It is just Spain's version of the Nato standard M855 5.56 rounds.