The Prado museum in Madrid has announced that it received a royal portrait recently attributed to Velázquez as a donation from an American art historian.

William B. Jordan, the art historian, said that he took his painting to the Prado’s art experts last year to have it authenticated after acquiring it in an auction in 1988.

The Prado said the portrait had been made by Velázquez as a preparatory painting for the face of King Philip III that became part of “The Expulsion of the Moriscos,” a masterwork completed in 1627 but that was destroyed in the fire of the palace of the Real Alcázar in Madrid in 1734. The work is known only from written descriptions as no copy has survived.