License, verbatimPD
The National Gallery of Art: open access image with no usage restrictions under the NGA's open access policy (openaccess=1 in the Gallery's published_images dataset).
Paul Gauguin. A Grazing Cow; Head of a Woman with Her Hand on Her Cheek, and Head of a Man with His Hand on His Ear [verso], 1884-1888. National Gallery of Art, Washington.