10 C. Postal stamp "Merkur head" and 90 C. Special stamps issue "world exhibition 1937 in Paris" with overprint in type I, correctly franked mixed franking on cover from "Ghyvelde 21.07.1940" to Dunkirk with reverse arrival postmark from "22.07.1940", faultless condition, expertise Lothar Herbst VP (2019: "the condition is perfect. The stamps are only in very small number of pieces known, therefore are they very rare. ", Michel 1.000.-