This is from a few years earlier than you requested, but in Rob Pike's "Unix History, An illustrated memoir" talk (https://m.youtube.com/watch?v=_2NI6t2r_Hs), at around ~11:18, Rob shows a photo of the University of Toronto's computer graphics lab (with Unix machines :P). He doesn't say the exact date, but based on context it should be from around 1979ish.

Hope this helps,

Josh