My first contact took place about 25 years ago on a system made by Convergent Technologies, it's unix flavor was called "ctix". After that was a short episode with a unix emulator running on PrimOS, the proprietary operating system by Prime Computers.
After that I worked with Sinix for some years, the Unix variant from Siemens, and a little bit with Xenix (SCO).
In 1995 I started to work with Solaris, version 2.4 was current at that time.
Between 1999 and 2001 I had a short encounter with Tru64 (Compaq). Somewhere around that time (I can't remember exactly) finally Linux sneeked into my professional life.
25 years of Unix and still reading manuals