Looks like maybe a home made adapter for the Perry carb?
Don't think it's plated just tumbled...

The 1st Tower engine was a Fox Eagle .60 Mk. 1
It had a bead blasted case, and a tumbled head, backplate and Perry carb adapter (cast )
I got one at their introductory price of $29.99 in IIRC 1976. I put it in a TF Contender and that was a nice combination.

I don't recall right off hand if Fox and Tower collaborated on any other engines during the 70's?