I forgot to mention another Exakta-mount lens I have. It's a 400mm f4.5 Piesker Tele-Picon (Berlin W. Germany) that I bought at a consignment shop a couple of years ago. Amazingly, I still haven't shot with it yet. The lens is very heavy, has a fixed lens hood with no threads for filters and has perhaps a single coating on the front element only. The aperture is beautifully round with 20 diaphragm leaves!
I will shoot with it soon.
Does anyone have experience with this or any other Piesker lenses?