This is what I know to be the earliest. I think they are Keystone Kustomags. The centers were not chromed. Some of the earliest center caps were just a script "K".
Around 1968 the Kustomags Klassic was the name given to the chromed center wheel. The center cap had a block "K" with Keystone in small lettering under it. A very popular wheel in the super stock class.
The third version, the Keystone Classic (or Klassic) has the spokes united with a thin ring and a tapered center cap. They mat have been made in direct lug pattern, but most of what you see is uni-lug. This is very similar to what Cragar offers, which is the picture I posted.