Carol II: the story of a stamped letter

An envelope with a Post Office stamp with the picture of King Caroll II, of Roumania, dated 9th April 1939. The war was too close. King's dictatorship close to the end.
I bought it to a street seller in OPorto.
Adressed to AKO, Zürich, sent from Cluj, Rua Regele Ferdinand, n.º 48. Today is here.