The advertisement from which your picture is taken does not propose more details; it simply reads: "Rometsch conversion - with 4 doors and extended chassis from the standard VW sedan". True that there's no specific mention of its exclusive use as a taxi, and I also found a mention of a Rometsch limousine, though I doubt seeing the inside of the taxicab that a partition could be installed, so I guess this is more a bad translation of German and is more likely a four-door saloon. If the pictured car has been intended for a more specific role, I do not know, so I cannot come up with a better answer than four-door saloon...