In 1940, Charles Wisner Barrell, a former director of Motion Pictures for the Western Electric Company, an American follower of Looney's and Allen's views, examined the portrait using X-ray and infra-red photography, and proved what Allen had suspected, namely that the painting had indeed been tampered with.
In late 1948/early 1949 a further series of X rays was made at the National Gallery of Art by Stephen S. Pichetto.