the "Kraftfahrzeuge und Panzer der Reichswehr" book, written by Mr. Werner Oswald, isbn 3-87943-161-2, Oct 1975, shows on page -86- and forward some variants of this beautiful car. It shows a Reichspost vehicle with RP licence plates on page -90-. Also, some colour variants seem to have existed, next to white a gloss black one without any license plate is shown, occupied by Mr. H. This vehicle was armoured and has a larger engine. Type G4 (W31) with a BD M24, 5019 cc, engine and the type G4 (W131) with a DB M 124, 5252 cc, engine. According to rumours only one vehicle survived the war.
By the way: anyone familiar with a technique to get a real polished chrome grill? This seems to be the main feature of this vehicle.