2.50 Fr. "war auxiliary work" with overprint in type I as franking on postage exceeding tariff rate cover from "Dunkerque 1. 7. 40" (first day) to Bourbourg with reverse arrival postmark from 2. 7. 40, stamp in perfect condition condition, cover right slight fold, signed Zierer and certificate with photograph autumn VP (2014) : "the stamps are only in very small number of pieces recorded, so that they very rare are. The postmark "Bourbourg" is very rare. ", Michel 1. 000.-