Thanks for the points and the comments.
Apparently there is a very nice article online about this car in German.
Google Translate offers this: "The engine came from a Simca 1000, the gearbox from the Porsche 356 Carrera. The vehicle had a double triangle wishbone front axle. The brake system and the wheel stars came from a Renault R8. The rims were made of aluminum. The race car weighed only 350 kilograms and always started in the 1000cc class"
Hirzel retired in 1968 "but in the same year the P17 appeared again in Hockenheim, but with Heinrich Baumgartner behind the wheel. At the Bergslalom Reitnau from 1969, the vehicle started with 1000 cc in the class "formula-free", driven by the new owner Max Rüetschi. The last entry in a ranking was at the slalom on the N1 of 1970, organized by ACS Aargau. The ACS organized again and again short term slalom on the pre-opening highway sections.
Now the P17 is being restored by racing driver and coachbuilder Ruedi Rohr from Hunzenschwil"
And here it is, the restored car at the 2012 Oldtimer GP in Mutschelle