License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Anonymous, Netherlandish, 15th century. The Angels of the Euphrates Killing Mankind; and The Angel Preventing Saint John from Recording the Words of the Seven Thunders, from an "Apocalypse" blockbook, second edition, 1440–50. The Metropolitan Museum of Art.