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).
Domenico di Polo di Angelo de' Vetri. Cosimo I de' Medici, 1519-1574, 2nd Duke of Florence 1537, later Grand Duke of Tuscany 1569 [reverse], c. 1541. National Gallery of Art, Washington.