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.

Oswald Theodor Baron von Hoyningen-Huene

I found a picture of him, and an article [in Portuguese] concerning his role in Portugal in cultural affairs.
German Amabassador in Portugal since 1934 and during the major part of WW2.
Facing him António Ferro, the Director of the Propaganda Services of the Regime. [for more, in Portuguese, here]