Often topping the lists of all-time great movies, and widely considered Orson Welles' best film, the only Oscar Welles was awarded for the 1941movie "Citizen Kane" will be auctioned Dec. 11 by Sotheby's and is predicted to fetch a price between 800,000 U.S. dollars and 1.2 million dollars.Welles won the Academy Award for screenwriting with Herman Mankiewicz. The movie about a power-hungry newspaper baron with political aspirations (rumored to be William Randolph Hearst) is one of the most critically acclaimed films of all time, which enhances the statuette's value, said Leila Dunbar, senior vice president at Sotheby's. "The movie had a star-studded cast. Welles was fearless in the filmmaking and he had complete autonomy, all of which helped him create a landmark movie," Dunbar said. The award was believed to have been lost until it surfaced at another Sotheby's auction in 1994 after being secretly held by a Los Angeles cinematographer who once worked with Welles and received it from him as payment. Welles' youngest daughter, Beatrice, sued Sotheby's and the cinematographer and eventually claimed the Oscar. When she tried to sell it, the academy sued her as part of its longstanding goal of keeping Oscars off commercial markets. Since 1950, the academy has required Oscar-winners to give it the first right of refusal to buy back an Oscar for 1 dollar. Because this particular Oscar had been given before 1950, among other reasons, Welles was able to prevail in court. In 2003, Welles sold the Oscar to the Dax Foundation, a Los Angeles-based nonprofit group that supports various educational, health and other causes. Dax is auctioning the Oscar. Dunbar said Welles' Oscar is hard to value because so few from classic or iconic movies come on the market. In 1999, the best picture Oscar for "Gone With the Wind" sold for more than 1.5 million dollars and Vivien Leigh's best actress statuette for the same movie fetched more than 550,000 dollars.