And right out of the blue comes the right answer!
Yes indeed, a 1969 prototype shown at the Frankfurt Motor Show by Metzeler, better known these days for making motorcycle tyres.
Here's some info. Please forgive any errors - my schoolboy French wasn't too bad 40 years ago, but I'm a bit out of practice now.
Metzeler Delta V
This manufacturer of tyres and car accessories introduced a first model in 1967, powered by a reworked NSU engine.
Its 130 bhp gave it a top speed of about 200 km/h. While it remained at the prototype stage, here to succeed it is this second version, the engine of which is more simply a VW 1500 Automatic. The base is also that of the saloon, the mechanical components retaining their original layout. The plastic bodywork is bolted on to the Volkswagen chassis. The top part of the roof is removable and folds into two for easy storage. The arrangement of the headlamps is different from that adopted for the previous prototype. You will recall that the entire front bonnet was raised by about fifteen centimetres to reveal a broad illuminated front panel consisting of six headlamps. On the Delta V the idea of this illuminated panel has been retained, but this time it is fixed, and it is the front part of the bonnet which pivots downwards to uncover them. This solution has the advantage of a very much simpler mechanism. This type of vehicle is intended to be distributed as a kit. This formula seems to interest a certain number of motorists who are anxious not to have a car for "Mr. Everybody"; but it is still necessary that the kit is easy to assemble. The success of this initiative may depend on it.
Marketed only in Germany, the bare shell is sold at 4,000 Deutschmarks.