
I know the basics, Bay of Kotor, (in Montenegro) was occupied by the Italians, and then the Germans, during WWII. Some Yugoslavian stamps, as well as Italian stamps, were overprinted for use there, but as far as I can find, no issues specifically designed for Kotor were made, officially. With the denomination in rpf (reichspfennig??), I assume it was issued later in WWII, during the German occupation.
any clue??