Cool.
My first Unix was some PC-based clone, the name of which I cannot remember now, but was also a while before Linux. Not sure whether it was before Xenix or not, though I used Xenix (SCO Xenix at the time, IIRC, or was it SCO Unix) a year or so later.
First Unix's name may have started with E-something. Everex? Not sure.
I think I also got to use Interactive Systems' PC Unix (PC-IX?) around the same time as the first one.
Soon after, moved to Unix on higher Motorola 680x0 processor based minicomputers, and even a multi-CPU SMP RISC Unix (from MIPS) for a while.
Later SVR3 and SVR4. Didn't like 4 though. By then (as I learned later) the UNIX wars had started, and it seemed to be a clunky hybrid of features from the SVR3 and BSD camps. Later worked a good amount on HP-UX too, on their PA-RISC business servers. Liked HP-UX. Pretty stable and powerful OS with a good patch management system and many other features and tools (HP PRM, Glance Plus, Ignite, MC/ServiceGuard, etc.).
The hp-ux mailing list was good too - very friendly and helpful people, I helped out others too.
Never got to work on Solaris, though, which I regret.
I remember I first wrote my selpg utility [1] on a HP-UX box (for a large corp customer, at their request), and then released it on the HP-UX mailing list. Some people appreciated it.
[1] http://jugad2.blogspot.in/2014/09/my-ibm-developerworks-arti...
http://jugad2.blogspot.in/2014/10/print-selected-text-pages-...
Good fun doing a lot of systems stuff on those machines for some years.