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 found in an upstate New York shed covered in bird droppings was discovered to be a rare piece of art.
• The work was identified as a live study by famed painter Anthony van Dyck dating back to the 17th century.
• The painting is expected to sell for between $2 million to $3 million, Sotheby's said.

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." 

The part-time art collector Albert B. Roberts, who recognized the importance of the painting, found it in a farm shed in Kinderhook, New York, in the late 20th century. 

Roberts, who bought the piece for $600, previously described his collection as "an orphanage for lost art that had suffered from neglect."  

He displayed the painting in what he described as "its pristine condition, happens to include bird droppings on the back," The Times of London reported, citing The Daily Gazette of Schenectady, New York.  

The Museum Boijmans Van Beuningen in Rotterdam, Netherlands, later showed the painting alongside, "Saint Jerome with an Angel." 

Susan Barnes, an art historian, identified the sketch as a Van Dyck and noted that the painting is "surprisingly well preserved," according to Sotheby's. 

Barnes said that the painting, which is nearly three feet tall, is one of only two of Van Dyck's live studies of such a scale that have survived, according to The Times. 

"They weren't really meant to be exhibited," Christopher Apostle, the head of the Old Master Paintings department at Sotheby's in New York, said, according to The Times. "The artist would often keep them in the studio to refer back to later."  

Roberts' estate is selling the painting next Thursday. A portion of proceeds will go to the Albert B. Roberts Foundation, which provides financial support to artists, other creatives, and charities.