3 Sgr. Postal stationery cover with single circle postmark POTSDAM 14.9. (56) to Dresden, on the back arrival stamp, there at the 15.9. With new address labels and having full margins 3 Ngr. Johann I franked and via Munich to Reichenhall sent on. Stamp with clear number postmark "1" cancelled, very decorative forward letter! Photo expertize Brettl BPP: "scarce and decorative two countries forward franking. " - probably the only one exists!