First time seeing these pictures. Dio could sing, no question about that. But there's really not much info about his bass playing. I guess he cared enough that he substantially modded his bass. Any ideas what the mods were/are? Are they some sort of jazz pickups? What about the toggles?
That's an early (1956) EB-0, this is an EB, which name changed to EB-1 when it was later reissued because of Felix Pappalardi.:
I would imagine people just naturally think the EB-0 was the first because of the zero but the EB was the first, most people call all of them EB-1's but they didn't get that name until the reissue and by then the EB-0 was already out so they had to name it the EB-1. The EB-2 is basically an ES-335 bass and the EB-3 is an EB-0 with two pickups.