To be completely accurate, the cross-and-circle marks is the NATO Design Mark. It's a pretty loosey-goosey thing. Despite it being on all kinds of ammo and boxes, it brings no guarantee of either proper size or proper performance. Nor does it mean that the ammo in question was made in a NATO country - I've seen Pakistan Ordnance Factory ammo with that mark. It merely means that the ammo is supposed to conform to the specifications of a Standing NATO Agreement or STANAG.
There is another one, the NATO Symbol of Interchangability, which looks rather like a four-bladed propeller. I've not seen it on ammo, but it's common on ammo containers and means that the ammo in question is interchangeable based on empiric testing.
"Interchangeability' means in this case that the ammo is safe, will function any weapon chambered for it and has 'adequate terminal effectiveness', all without having to repackage it (eg move it into different magazines or belts), adjust the weapon, make major changes to the sights and having about the same range.
And, yes, it was made in 1977 by Fabrique Nationale in Belgium. It is undoubtedly military ammo.