'Nu adosse 1' was featured in de Lempicka's first major exhibition in 1925 in Milan, after which its whereabouts went virtually unknown -- until a few months ago.

The artist's catalogue raisonne, published in 1999, listed the painting with the designation "location unknown."

The consignor, a West Coast construction company owner, had the 1925 work in his home for a decade before an art consultant recommended contacting the auction house, according to Sotheby's.

The owner "had no inkling of what it was," said Simon Shaw, Sotheby's head of Impressionist and modern art, explaining that Lempicka was Polish and sometimes signed her work "Lempinski," as was the case with "Nu adosse 1."

The auction house was able to verify the work's authenticity in large part because Lempicka's 1925 exhibition had been photographed.

"It's rare that you can actually prove that a picture is this great, long lost work as a result of a gallery installation photograph, as in this case," Shaw said.

Shaw said the piece was a classic Lempicka, noting its Art Deco esthetic and depiction of 1920s-era female sexuality, which is so endemic to her work.

"It's very clean, elegant and glamorous, and epitomizes her work," he said.

Prices for works by Lempicka have soared in recent years, with her auction record having been broken twice in just the past year alone. "Le reve" soared past its $6 million estimate to fetch $8.5 million at Sotheby's in November.

"Nu adosse I" is estimated at $3 million to $5 million, but estimates do not include commissions that drive the gavel price up another 12 percent.

Shaw noted that there are few female artists within the Impressionist and modern field at that level.

"She is now one of the most desirable of all female modern artists," he said.

Lempicka, who died in 1980 aged 81, peaked relatively early in Paris during the 1920s and 1930s, and became a favorite of the Hollywood set, eventually settling in California for a time. She spent most of her last decades living the life of a glamorous European socialite.

Today, continuing a resurgence that began shortly before her death, Lempicka remains popular in Hollywood, with collectors including Barbra Streisand, Jack Nicholson and Madonna, who has featured several of her works in her videos, movies and stage shows.

(Reporting by Chris Michaud; editing by Patricia Reaney)

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