The Oscar Orson Welles won for Citizen Kane 70 years ago will go up for auction online this month, a Los Angeles auction house announced Monday.

The statuette has had a chequered history. It was thought lost for years and failed to sell at auction in 2007. Previously, it was the subject of a lawsuit by the U.S. Academy of Motion Picture Arts and Sciences, which claims ownership of all Oscars that leave the hands of the winners themselves.

Auction house Nate D. Sanders has set a reserve price of between $600,000 and $1 million US for Welles' best screenplay Academy Award. The auction is set for Dec. 20.

The actor, director and star of Citizen Kane was 25 when he released the now-classic film about a ruthless newspaper baron. The American Film Institute named Citizen Kane the top film of the 20th century and it was nominated for nine Academy Awards, including best picture, in 1942. However, it won only best screenplay for Welles, in association with Herman J. Mankiewicz.

Welles was neglected by the academy for the next 30 years, until he earned an honorary award "for superlative artistry and versatility in the creation of motion pictures."

Challenge to sales

The academy challenges efforts to sell Oscar statuettes and was successful three years ago in stopping the sale of two Oscars awarded to silent film star Mary Pickford.

Orson Welles' 1941 Oscar for best screenplay for Citizen Kane is shown in 2007, when it failed to sell at auction. (Frank Franklin II/Sothebys/Associated Press)However, auction house spokesman Sam Heller says a judge cleared the way for this month's sale with a 2004 ruling that Welles never signed the academy's agreement not to sell the trophy.

Welles’ Oscar was thought lost for years, but the golden statuette resurfaced when it was put up for auction in 1994 by a cinematographer who claimed the filmmaker had given it to him as a form of payment.

Welles' daughter Beatrice sued and won ownership of the Oscar. But when she herself tried to sell it in 2003, she was sued by the academy. The organization cited a rule, enacted in 1950, that it must be given first rights to acquire any Oscar hardware put up for sale (and for a nominal sum).

That legal battle resulted in the 2004 court ruling and Welles' daughter quietly sold the award to California nonprofit the Dax Foundation, which in turn was unsuccessful in selling it at auction in 2007.

Experts at auctioneer Nate D. Sanders believe there is now strong international interest in Welles' Oscar. In 1999, Michael Jackson paid $1.54 million US for the best picture Oscar awarded to the 1939 film Gone with the Wind at an auction the academy was unable to block.