Stamps of Maribor provisional issue were used internally as porto provisorium before and after the end of general validity.
1945 Guštanj porto provisorium, letter sent from Ljubljana (29.6.45) to Guštanj (2.7.45) with arrival postage due stamps (24 pf) cancelled with "Guštanj," / "PORTO / -2.7.45".
1945 Guštanj porto provisorium, letter sent from Ljubljana (2.7.45) to Dravograd, forwarded to Guštanj with arrival postage due stamps (24 pf) cancelled with "Guštanj," / "PORTO".
