As far as I'm aware, there are no `measurements' I remember when I went to buy mine from `Speedwheels' in Leicester in `83/84, they had a batch of 10 in a line, no two were the same, apart from the mucky fingerprints under the vinyl!!
Some had the fork stickers one way up, some the other, I made sure I had dirty hands when I put mine on for authenticity!!
Mark M