‘Star Wars’ 1st birthday poster, 1978.
Fantastic find! Thanks!
This was a thing because the first release of Star Wars stayed in theaters for 18 months! First from May 25, 1977 to July 20, 1978, then extended to November 7. There were also multiple re-releases (detailed in a surprising overview at starwars.com).
In the days before home viewing, this was how you built the fandom – studios leaving movies where fans could watch ‘em, and fans watching repeatedly.
This was quite a bit longer than usual, of course, and being in theaters a year later was definitely worth celebrating.