[TUHS] Likelihood of Extant Less-Distributed Tapes and Sources

Good morning everyone. Wanted to pose the question since folks here would probably be more likely to know than anyone. What are the chances that there are surviving tapes of some of the UNIX versions that weren't so well publicized. The versions that come to mind are the CB and USG lines especially, with PWB 2.0 and TS 4.0 getting honorable mention. If folks will recall, we did luck out in that Arnold, a member of this mailing list, did have a documentation trove from TS 4.0, but no binary or source code assets. This had me curious on what trying to unearth these would even look like. Has anyone tried to dive deep on this sort of stuff before? Would it look more like trying to find old Bell facilities that might have a tape bumping around in a box in a basement somewhere, or is it more likely that if anything survived it would have been due to being nabbed by an employee or contractor before disposal? Or even just in general, what would folks say is the likelihood that there is a recoverable tape of any of this material just waiting to see the light of day? The closest we have on CB is a paper scan of the kernel sources, and I don't know that any assets from USG-proper have ever percolated up, closest thing to any of that would be the kernel routine description bumping around on the archive somewhere. PWB 2.0 is mentioned in several places, but no empirical evidence has surfaced as far as I know, and with 4.0 of course we have the documents Arnold thankfully preserved, but that's it. Thanks in advance for any insight or thoughts. My concern is that there is a rapidly closing window on ever being able to properly preserve these parts of the UNIX story, although recognition must be paid to all of the hard work folks have done here thus far to keep this valuable part of computing history in the collective consciousness and accessible to researchers and programmers for years and years to come. - Matt G. P.S. Even more honorable mention is the Bell Interdata 8/32 work. I've read several places that never saw outside distribution, but I would have to wonder if any of that work survived beyond the visible portability changes in V7.