I stumbled accross this interesting article. The only Isdera Commendatore is up for sale on eBay.
I found an article on Supercars.net, that pretty much sums it up. See 'source' below.

This is a beautifull car, IMO. Same shape as the XJ220. When looking at the front of the car, you can see the destinguished look of PORSCHE. After all, it was Eberhard Shultz, former PORSCHE designer who made this car a reality.

BTW, this prototype is in full working order.

Click to view attachment


Source

Adieu