She called it her worst-ever movie. But even in the film she considered her greatest failure, Marilyn Monroe was as spectacular as ever. Now the iconic dress the silver screen star wore in 'River of No Return has sold to a private buyer for $504,000. Darren Julien, president and CEO of Juliens Auctions, said Saturday that the dress was sold at an auction in China. Monroe wore the green velour dress while she sang 'Im Gonna File My Claim in the 1954 Western in which she portrayed Kay Washington, a gamblers wife. The film, in which Robert Mitchum starred alongside Monroe, follows the fortunes of a gunslinger released from jail and trying to start a new life with his 10-year-old son. Its production was marred by conflict between the director, Otto Preminger, and Monroes acting coach, Natasha Lytess, who insisted the blonde bombshell enunciate every single syllable of the script with exaggerated emphasis. DM Premingers experience on the film convinced him he never wanted to work for a studio again, and he left for Europe before the post-production was complete. The film received a lukewarm reception from the critics, who in the main agreed that the best thing about it was Monroes screen presence.