Thanks for the pictures. By the construction it appears to be an aftermarket baby moon cap and may fit several makes of cars hot rod style. The earliest Kaiser or Frazer cap with the lettering fit on knobs that were built into the rim much like the '40-'48 Fords and Mercury's. The regular '47-48 caps were held on by clips on the wheel. The early caps are difficult to install without denting them. They were much like the early Camaro small caps that were almost impossible to install without denting the cap. They were aluminum. Another of GM's "Better Ideas".