Sotheby's New York said it will sell three ``rediscovered'' Russian modernist masterpieces from the collection of an American museum that may net as much as $10.3 million in a November auction.

The three paintings by Boris Grigoriev belong to the Berkshire Museum in Pittsfield, Massachusetts. Outside experts hadn't seen the works since 1948 when they were given to the museum by two collectors, Josephine B. Crane and her sister, Florence B. Keep.

Berkshire Museum said it aims to tap demand for Russian art by a new class of rich Russian and Ukrainian buyers, and to spend the proceeds on new art works and pay for the upkeep of its existing collection.

``These paintings have never been exhibited to our knowledge, and we have no plans to develop holdings of Russian art, nor is there another logical context in our collection for them,'' said Stuart A. Chase, executive director of the Berkshire Museum in an e-mailed statement. ``They present an opportunity for new acquisitions that will enhance the future of the institution.''

The museum has more than 30,000 objects including ancient Egyptian artifacts, American paintings, and a dinosaur gallery.

The Grigoriev paintings will be sold with about ``20 to 30 other art works'' in New York on November 4, Sotheby's said. The auction house usually only has one New York Russian sale a year, in April.

Peasant Musicians

The top lot ``Pipe Players'' (circa 1920s), has an estimate of $4 million to $6 million. The 7-foot work, one of Grigoriev's largest oil paintings, shows peasant musicians performing folk songs. ``Man with Pipe'' (circa 1920s) has an estimate of $600,000 to $800,000. ``Shepherd of the Hills'' (1920) has an estimate of $2.5 million to $3.5 million.

``These rediscovered works are the most important Grigoriev paintings to appear on the market, with the exception of one work from the Rostropovich-Vishnevskaya collection,'' said Sotheby's New York director of Russian paintings Sonya Bekkerman, referring to Grigoriev's ``Faces of Russia'' (1921).

The Rostropovich-Vishnevskaya collection was bought by Russian billionaire Alisher Usmanov in September at Sotheby's London.

Sotheby's is the market leader of Russian art; it reported a 24 percent rise in 2007 sales to $190.9 million, a 31-fold increase over 2000. Earlier this month, Sotheby's London sold 39.72 million pounds of Russian art.