These are the early center cap wheels and the valve stem on early ones also were in the face like on a Cragar. Mid 1970's seems to be the point where the wheels got the valve stem between the spokes.
I believe the earlier ones, like 1965~1967/8 had a more silver painted area and the later ones used black paint. I would guess these to be 1970. I want a set, but don't own any yet. You said a date code is no obvious?
