They are aftermarket high compression pistons made for 1953 and later engines using the 819 head. These look like they have a pretty large crown and would produce a very high compression ratio. Quite a few manufacturers made them years ago. I ordered quite a few of them 50 to 65 years ago from Warshawsky Bros which is now JC Whitney. I think finding one with the same compression ratio would be next to impossible. They were never very popular. It was easier to bolt a 270 or a 302 engine in and get more hp on regular gas instead of going to higher compression requiring higher octane.
