I just acquired an early 70s SSB kit (serial numbers put the toms at 1970 - the BD is a RB from '66). From what I can tell the shells are exactly the same as RB but the SSB toms have vent holes, where RB had the tack badge. As for the sound and function, I don't see any difference between my toms and RB toms. I'm fortunate enough to have toms that have no head fit issues and even modern heads slide right on. I've heard this is because at that point the head fit issue was solved, but I've also heard when production moved to Baldwin there was some issue with quality control. Both could be true…or false. But from what I can see, very early SSB toms are the same RB shells, just with air vents.
That said, the head fit thing may vary from kit to kit till you get into the 70s, but mine sound like RBs. Sound best tuned medium to high, but luckily they can be tuned low without wrinkles which is an issue with many RB toms.
I'm no Gretsch expert, just speaking from my experience. Good luck!