"Pawn Stars" is about a family-run Vegas pawn shop that buys unusual objects after verifying their worth.
The Las Vegas Sun said Diane Hutton went on the reality show to see what she could get for the script, which was dated 1971, autographed by someone named "Al" and donated to her Catholic Charities shop.
The classic gangster picture starred Al Pacino, Robert Duvall, James Caan and Marlon Brando.
"I told people around me, 'Let's see if we can find anyone who can authenticate the signature,' and one of the girls said we should take it to 'Pawn Stars,'" Hutton told the newspaper, explaining how she and three others headed off to the famous store featured on the show.
Hutton said the series' stars Rick Harrison and Austin "Chumlee" Russell verified the autograph was Pacino's and offered her $500 for the script, a price Hutton felt was too low for such a piece of memorabilia, the Sun said.
Hutton said she hopes to get a better offer in the future.