You were probably wondering why I didn't jump at Uli's nice floater - quite simply, I didn't know it ! Apart from that rather curious and sadly incomplete 'yellow' website, there is not much info on inter-war German aviation, at least not in English.
Well I do have the full story on Robert's twin-boomer. It's the first prototype - F-AKCA - of the SPCA III. (the second prototype had wing fillets on the trailing edge). Mike (Pommehomme) kindly obtained for me a copy of Yves Laget's excellent SPCA book, and my French is just about good enough....