A painting covered in bird droppings found in a barn in upstate New York turned out to be a rare work of art that is expected to be sold at a Sotheby's auction next week for $3 million, BI reported.

According to the auction house, the painting, which depicts a bearded elderly man sitting naked on a stool, has been identified as a sketch by the famous 17th century Flemish painter Anthony van Dyck. The work, believed to date from between 1615 and 1618, was a sketch for Van Dyck's painting St. Jerome with the Angel.

Art collector Albert B. Roberts, who realized the importance of the painting, found it in a barn on a farm in Kinderhook, New York, in the late 20th century.

Roberts, who bought the piece for $600, had previously described his collection as a haven for lost art that has suffered from neglect.