z77

I've a set of swaztika wheels and from what I can tell is all the early aluminum wheel have the same center cap, but was corrected on this, that there are different diameters.
question what z were this originally found on and does the cap have a cirle around the Z or not, and are these a plastic or metal
and if somone has the part number from nissan all the better.
Thanx
Z77