Bill,
To try to answer your questions:
Yes, luxury cars were still in limited production, such as the Grosser Mercedes and Horch models. They were at this time, probably only available to the Nazi party or wealthy folk with plenty of political clout.
Take a close look at the hood, hood sides, and windshield frame. You will see these are the same, if not very close to the sport cabriolet. Slight differences exist in Horch models, as these were after all expensive bespoke automobiles.
The information I have gathered states that the original body of the car was removed and discarded, and the current, 4 door monstrosity created.
The reason the car is virtually unrecognizable in it's current guise is due to the original grill shell having been discarded when the front mounted pump was installed. In an effort to "modernize" the car, as well as protect the front pump, the flip front was designed, with it's heavy Buick-esque grille teeth.
The front and rear fenders were reworked to "update" the vehicle somewhat to late 1940's styling. Have a look at a DKW and you will see that the headlight placement is about the same. For all we know, DKW headlights were probably used in the conversion.
Also keep in mind that this car was little more than a war prize when it was converted. It was probably assigned or given to the fire department, and for all we know, they were probably allocated funding to do the conversion. Many Grosser Mercedes, and Horch automobiles sent to the Soviet Union were either cherished by the enlightened party officials, or turned into tractors by farmers having no practical use for a luxury car.
Many 1930's V12 or V16 Cadillacs wound up as tow trucks, fire pumpers, or snow plows when they fell out of fashion. If you recall the early 1930's V16 Cadillac ambulance that was auctioned a few months ago, it had also been modified from it's original configuration and made to look more modern, with skirted fenders and updated grill shell.
After WWII, the last thing you would probably want to be seen in was a Horch or Mercedes that belonged to the Nazi party. Here in the USA, however, many of these cars were brought over as war prizes, and it was quite "cool" to have one as a toy. The late Bob Hope had tons of Nazi memorabilia, including staff cars, touring cars, etc... all no doubt given to him during his tours entertaining the troops.
As to the pumper unit in front of the car, it was probably not too difficult to adapt this, as it is possible that this engine shared components with industrial engines or military applications. Keep in mind that individuals of any country emerging from a devastating war, will become very resourceful beings if the need arises.
While I have no idea why such a futuristic plexi glass covered body was needed, I'm certain there was some reasoning behind it. The important thing is that the car has survived, and will one day be restored into a proper Horch once again. European craftsmen are some of the most highly trained in the world, and I have personally seen them bring back cars where only a frame or engine were present.
While not a pro car by our definition, I am glad that this vehicle was brought to our attention, at the very least, it makes for interesting discussion
