German offical postal service Ostland, 5 pfennigs postal stamp with overprint Ostland in mixed franking with 10, 12, 20 and 60 pfennigs postal stamps with overprint Ostland, on correct franked registered air mail letter to Bleckede, registration label with single line cancel "Pleskau" and official seal of the post office Pleskau, cancelled "PCKOB * K * -1 6 42, reverse arrival postmark Bleckede, photo expertize Robert Brunel VP (2025) "small tiny stain spots