Pioneer Flight covers. 1942, inverted black overprint ''Africa Française Libre'' on 2.50fr green and buff, used together with overprinted 8.50fr red brown and yellow on air mail registered cover from Fort-Lamy (now - N'Djamena) to Douala (Cameroon), French censorship tape and markings, VF and rare, C.v. $275 for stamp only (Image)