Unfortunately I haven't seen this one before, so just some thoughts from me. At first sight one is tempted to say that it is another VW Kübelwagen based private one-off, but the wheels don't look VW to me. What I can't really identify is the bulge above the license plate. Is there a single headlight or just a sign? Is it an air intake for a front engine? The round objects besides the license plate look like horns. It seems as if the windscreen wiper axles go through the glass what is quite uncommon on German cars. For the year the picture was taken I would think of 1951/52 going by the VWs, the Fiat 1400 Cabriolet and the license plates. The location probably in the Southwestern part of Germany, as the (hard to identify) first letters on the plate don't look like AB for Bavaria.