4, 50 Fr. postal stamp with overprint "fortress Lorient" as a single franking (postage exceeding tariff rate) on cover from the "fortress Lorient 20. April 1945" to La Baule with reverse arrival postmark from 30. 4 45, the cover was poste restante mailed and at destination "La Baule" was the post storage fee of 1 Fr. later calculated and with the red machine cancel receipted, without any engraverãs mark and photo expertize Lothar autumn VP (2015) : "the condition is perfect. A nice cover. The stamp has only a very small issue from 100 pieces. Covers of the fortress post Lorient are general very rare. So far are from of this stamp only 4 covers registered, the all over franked single frankings are and in the fortress St. Nazaire used are. Therefore an extreme rare cover. "