Glaxo decided to sell works at a substantial discount to employees and to put the rest up for auction, with the notable exception of the Wyeth.
Robert W. Carr, GSK senior vice president for environment, health, and safety, said proceeds would go to local charities.
Painted in 1929, the Wyeth depicts a dramatic moment in The Odyssey. A powerful Odysseus has returned home from decades of war and wandering, and is about to shoot an arrow from his mammoth old bow through a tunnel formed by a series of curved ax heads. A crowd of assorted interlopers and moochers looks on, interested but so far unaware that the bow will be turned on them.
"This is a moment of revelation," said Kathleen Foster, the museum's curator of American art. "It takes genius to seize the right moment" in a story, she said, referring to Wyeth's prolific career as a highly sought-after illustrator. "He was so good at that."
The painting, The Trial of the Bow, is one of 16 made by Wyeth to accompany a new edition of Homer. The Odyssey series was sold to a collector in 1930 by the artist, who lived in Chadds Ford with his family, including his son, the painter Andrew Wyeth.
The paintings were subsequently scattered, and most have yet to be located. A trove of Wyeth family art is held by the Brandywine Museum in Chadds Ford, a fact that has served to attract even more Wyeths to that institution, said Foster.
The Philadelphia museum, though it owns four Andrew Wyeth paintings, has hardly had a chance to get past the Wyeth family door, she said.
Glaxo acquired The Trial of the Bow in the 1980s, said Millora, amid circumstances that are unclear.
In addition to the Wyeth, the museum also announced several other gifts, including four 18th-century paintings currently in the exhibition "Journeys to New Worlds: Spanish and Portuguese Colonial Art from the Roberta and Richard Huber Collection," on view in the Perelman building.
The paintings include King Luis I of Spain on Horseback, from Peru; Saint Anthony of Padua Preaching Before Pope Gregory IX, also from Peru; The House at Nazareth, from Bolivia; and Our Lady of the Reedbed of Irún With Donor, Captain Joaquín Elorrieta, painted by the Ecuadorean artist José Cortés de Alcocer.
The museum also acquired Redouté's Amaryllis Josephine, a double-page watercolor on vellum, accompanied by a pencil drawing of the flower bulb, and a stained-glass-and-bronze chandelier made about 1905 by Tiffany Studios.
More than 220 images by the American photographer Paul Strand were acquired at the end of 2012.
Timothy Rub, museum director, noted that more than 90 percent of the museum's almost 227,000 artworks entered the collection by donation, a fact that the recent acquisitions underscored.
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