Oh hell that's a cap off of a '53 Trojan, you can tell by the horse. pretty rare, the cars were ****py and they ended up in the condom industry.
Looks like an aftermarket unlicensed copy of a Mustang II hubcap. As BJR said, the copies were often chromed steel, cheaper to make in short runs than stainless ones, and just slight variances to make sure they're not design patent protected. Is it 13"?
I'd go along with JC Whtney. They used to have page upon page of "almost look like" replacement hubcaps along with page after page of mirrors and other trinkets.