"Sotheby’s called it 'undoubtedly a forgery' based on research conducted by Orion Analytical, a scientific analysis firm that Sotheby’s acquired last year"

NYT:   Sotheby’s Files Second Lawsuit Over Works It Calls Fake.

"[Orion's] Mr. Martin said that he took 21 paint samples from many different areas of the paint layer and found the 20th-century pigment throughout the work, including in areas of the painting that were never restored. 'It’s a bit like taking the pulse of a corpse 21 times,' he said."