Renames refer to movie posters that were released prior to a movie opening and where the movie had its name changed to something else. When this change is made, movie studios try to recall all the early advertising material with the early title (or working title) of the movie.
Renames can be highly sought after because of their rarity. While it doesn't happen often, in the case of Star Wars Episode VI, a lot of movie posters were sent out with an early name - Revenge of the Jedi.
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