I never took those kinds of notes. We certainly talked about it and we used to have know who had what at Locus since all of the majors were our customers and we had to be very, very careful to not cross pollinate. Sometimes we would do specific work in different offices, just to make the firewall easier to manage. For instance the Ultrix and Tru64 work we did for DEC, as well as the HP work was done in Boston. Most of the IBM work was done in the LA office, and Intel work was led in San Diego.
There was a time when I had the release schedules of DEC, IBM, HP and Sun taped the wall behind my desk, because we had teams delivering things to all 4 of them.
That said, if you talked to one of the UNIX press of the old days, like the old "UNIXgram/X" folks, you could put together the chronology. However, I don't know that any of that is on line anywhere to search. But that would be the documentation I would look if I was a lawyer trying to demonstrate who did what in what order. Some of those folks are still around and writing, I saw something from Timothy Pickering Morgan just yesterday talking about Linux and I see some of the other names pop up in the blogs and journals at different times.