The prototype of the Raab-Katzenstein RK 25. The third of three examples built, D-1701, also took part in the 1929 Challenge International de Tourisme and is seen on the far left wearing start number B3. B5 is the Akaflieg Darmstadt D 18, D-1561. The third aircraft is a BFW M 23, D-1711 / A9, flown by Alexander von Bismarck and wearing his famous family name. I-AANH / K3 is again in the background. Photo from: Bibliothèque nationale de France - Gallica