6. South America flight 1933, registered letter from Boutilimit 5.8. To Buenos Aires with 10 Fr overprint provisional arrangement, 1, 50 and 2 Fr landscapes in colourful mixed franking, via Dakar / Senegal 14.8. And Paris 21.8. To Friedrichshafen with transit 2.9, flight stamp on face, arrival Buenos Aires 7.9, rare small place of posting inside from Mauritania and general extremely scarce, exotic incoming line, only a few documents from Mauritania ever known, ex Buchal (winner 239)