50 C. Charity issue \"Musica with new overprinted value+20 C. \" with overprint in type I, vertical pair with variety \"inverted overprint\", properly franked multiple franking on letter from Ghyvelde 15.7.1940 with on the back arrival stamp from 16.07.1940, 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. Multiple franking with charity stamps, to boot with inverted overprint, are extremely rare. \", Michel 1.800.-