This prop was produced for the Star Wars Prequel Trilogy (Revenge of the Sith) films, to be backlit on the Senate Pods. Each one is a sheet of printed transparent soft acetate, 210mm x 285mm (A4 size, approx 11.5 inches x 8.5 inches). The vendor explained me :
"We ran a prop house which supplied a great deal of stuff for the prequel trilogy, and after principal photography at Leavesden was completed, these came back along with everything else. They were indeed produced for the prequel trilogy but I cannot guarantee they are SOS"
As I can't establish provenance for sure, I list as replica, but I believe it's an original.
More from Star Wars: Episode IV - A New Hope (1977)