Here's another clue as to the origin of the two posters - I've been in
touch with the seller and she tells me they were purchased (though not
necessarily published) through UNIX Review magazine. I can't find a
first-publication date for that mag but I think the poster ad (now
deleted) says the posters were (C) 1983. Did UNIX Review go back that
far?
Also, the posters are glue-mounted to a board, which will make
scanning difficult :(
-j