An oil painting that was discovered in a farm shed covered in bird droppings is a rare piece of art expected to sell for up to $3 million

An oil painting covered in bird droppings found in an upstate New York shed is a rare piece of art expected to fetch up to $3 million in a Sotheby's sale next week. 
The painting, which depicts a bearded, older man sitting nude on a stool, has been identified as a live study by the famed 17th-century Flemish painter Anthony van Dyck, the auction house said. 
The sketch, which is believed to date back to between 1615 and 1618, was a study for Van Dyck's painting, "Saint Jerome with an Angel." 
An oil painting that was discovered in a farm shed covered in bird droppings is a rare piece of art expected to sell for up to $3 million