The iconic ivory halter dress is the same one that went billowing up over her legs as she stood on a New York subway grate in the 1955 film "The Seven-Year Itch."
The Monroe dress is among more than 500 costumes Reynolds acquired over the years and placed on the block Saturday in Beverly Hills.
The catalogue also includes some well-known garments such as the gingham dress Judy Garland wore for her "Wizard of Oz" tests, and the modest frock Julie Andrews was dressed in for the opening scene of "The Sound of Music."
Britain's The Daily Telegraph said the auction was one of the most important sales of Hollywood memorabilia since the liquidation of the inventory at MGM and Fox studios in the 1970s.
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