I have a box of 6MM Remington ammo that I know is 1970 vintage, because thats when I bought the rifle. The box is green and white, and the primers are gold. Also have several boxes in the old green and white(3 boxes to be exact), in 3006 and they also have the gold primers. I don't recall ever seeing any Remington ammo from 1968 on that didn't have gold primers. Prior to 1968, I can't tell you, as that was before my time, but I'd be inclined to think you have handloads if they are silver primers, just my personal opinion.