Lots of greenwashing going on here too. The nordic countries are just as capitalist as anywhere else, we just had a strong labour movement in the 19th and 20th century. And sadly, a lot of what was won has been slowly whittling away in the last decades due to the complacency and inaction of the generations after.
Byrne began drawing X-men in 1977 (Uncanny X-men #108), and the brown suit was introduced in #139 (nov 1980) so 70s is definitely your best bet here. (This is 100% a Byrne panel.)
Edit: I had a hunch and found the issue, it’s from #125 september 1979, page 6 (“The perils of the Danger Room!”).