25 C. Mercury blue-green, block of four with two vertically overprinted pairs, correct 1 Fr. franking on letter "Dunkerque 2.8.40" to Malo les Bains, arrival 3.8.40, envelope transit wear, stamps perfect, signed Roumet, Lothar Herbst VP expert opinion (2025): "Stamps faultless. Issued in very small printing of 800 pairs.", Mi. 2.100.-