25 C. Postal stamp "Merkur head" with overprint in type I, common, vertical over all fours stamps walking overprint, correctly franked more franking on cover from "Ghyvelde 30.07.1940" to Dunkerque with reverse arrival postmark from "31.07.1940", faultless condition, franking top right little gum spots, expertise Lothar Herbst VP (2018) : "the other condition is perfect. The stamps are only in very small number of pieces known, therefore are they very rare. ", Michel 1.000.-