I was delighted to hear that a tape of #UNIX V4 has been successfully recovered & its contents made available for posterity. This was a really primitive OS but it laid out the path for decades to come in the IT sector.
https://www.theregister.com/2025/12/23/unix_v4_tape_successfully_recovered/ has more on this recent success story.

I just went through an installation of that version on a simh PDP-11, placing it next to several other historically significant UNIX versions, as shown in this quick screenshot.