50 C. "Mercury Head" definitive, "Occupied Territory Northern France" overprint type I, correct franking on local letter "Dunkerque 1 7 40" (first day), arrival 2.7.1940 on reverse, perfect condition, expertised H. Krause, Pickenpack BPP, Lothar Herbst VP expert opinion (2025) "Condition faultless.", Mi. 600.-