Liam Neeson, who played Jedi master Qui-Gon Jinn, donated the poster to raise funds for the Highdown School, a school for students with special needs in Worthing, U.K. Neeson's nephew, who has Down Syndrome, attends the school.

In addition to Lucas and Neeson, the poster is also signed by Natalie Portman (Queen Amidala), Jake Lloyd (Anakin Skywalker), Samuel L. Jackson (Jet Master Mace Windu), Ahmed Best (Jar Jar Binks), and co-producer Rick McCallum.

As of 6:30 AM ET today, 11 people had bid on the poster, with the latest bid topping out at $4,400. Organizers expected the bidding to go as high as 50,000 pounds ($78,000).

Promotional posters are generally displayed in movie theaters, which are supposed to return the posters to Lucasfilm to be destroyed after the movie stops showing. While movie theater workers have been known to keep copies, they'll have a hard time getting another copy with all those autographs, making this poster a one-of-a-kind.

(Reuters contributed to this report)