Other things that are queer:
Two input jacks - the recessed dish is the right part, but 215 Bassmans only had one input jack, and it was in the upper right corner, as viewed from the rear with the cab stood up vertically.
The 215 Bassman cab had amp mounting studs - both on the top and on one side. It also had three strap handles on one long side.
The serial number plate is authentic, if not to this cab. IIRC, they were held on with small rivets, not screws, but I don't think that's necessarily an indication of anything - the cab could very well have been recovered.
If it ever was a Bassman cab, the baffle board has definitely undergone some modifications. The ports are not stock and no Fender cabs had front-mounted drivers.
That does indeed appear to be an early-era Peavey grill.
Interestingly, the drivers look as if they really are EVs.
I'm still waiting to hear if it's 11-1/2" deep.
My vote is it never was a Basman cab. Peavey seems likely, or shop-built.
Edit: Still another indication is that Fenders all had removable backs.