For Revenge of the Jedi, you'll need to look at the lower right corner of the poster, to see if it is one of the popular reprints. The poster pictured is real .. for a fake, you'd see a bit of cloud or fade in the corner, by the Fox logo. Authentic copies of the poster measure 40.75" to 41" .. as the poster is frequently folded, there are differences in the accurate measurement of the paper.

An authentic Revenge poster with the date teaser at the bottom will sell for $400 (folded) up to $1000 (rolled) at auction.