The FNMT-RCM, in addition to printing philatelic products, collaborates with the Postal Service in creating jointly-produced sets of collector coins and stamps.

To mark the occasion of the "75th Birthday of Their Royal Highnesses the King and Queen of Spain", we issued the artist's proof of the souvenir sheet of stamps that commemorates this anniversary. Featured on the proof is the reproduction in silver of the postage stamp dedicated to Their Majesties.

The proof presents a view of Madrid's Royal Palace, the King's coat-of-arms, and a portrait of the monarchs, designed as an homage to the 75th Birthday of Their Highnesses the King and Queen of Spain.

Juan Carlos of Bourbon and Sofia of Greece, who were to become Spain's monarchs 37 years later, were both born in 1938, with just a ten months difference in time.