A formerly unseen work by Joan Mitchell led the Bonhams postwar and contemporary art sale in London today. The untitled abstract oil painting, a triptych dated 1975–76, sold within its estimate for £278,500 ($445,909), in the sale at which 77.5 percent of the 40 lots sold. The total sale brought in £1,765,250 ($2,826,360) just over its low estimate of £1.6 million ($2.6 million).

At 13-by-25 inches, Mitchell’s painting was smaller than the mammoth canvases she was known to paint in the early years of her career. It had been a gift to her good friend Patricia Molloy, who had shared Mitchell’s East Village studio. Molloy passed the painting on to her heirs.

Since 2004, her paintings have been selling in the millions. This May, the late artist became the most expensive female artist at auction when an untitled painting from 1960, a 90-by-80.2-inch canvas, sold for $11.9 million. Another unseen canvas that was a gift to Molloy was also in the sale. It was also within the top 10 lots at auction when it sold within its estimate for £116,500 ($186,529).

Other top-selling works were an eclectic group which included Gerhard Richter‘s diptych Rot-Blau-Gelb (338-11, 338-21) (1973), which sold for £194,500 ($311,416) within its estimate of £160,000-£220-000 ($256,178-$352,244); a stabile by Alexander Calder that sold for £182,500 ($292,203), exceeding its high estimate of £150,000 ($240,167); a work on paper by William Kentridge entitled An Embarkation, which exceeded its estimate when it brought in £134,500 ($215,349); and a red Banksy painting featuring Argentine revolutionary Che Guevara on skates, which sold for £86,500 ($138,496), exceeding its high estimate of £80,000 ($128,089).

The sale also featured work by David Ostrowski, Bridget Riley, and French artist JR.