The last one is outstanding Bogotron
I had the IV Summicron for a few years. It was my favourite lens on my M6. I recently traded it, and got a Voigtlander 35mm f1.4 I am very happy with. The IV crom was great, but it ended up literally falling to bits. I bought it used, well used, and I used it a lot, so got my money's worth from it. The worst think was the focussing tab which kept falling off and breaking. And I never got on with the lens hood or silly hood cap which kept falling off.
It as great for black & white, but I can't say I got spectacular colour from it.
I have just bought a Zeiss Ikon ZM, and decided to buy the 35mm f2 Biogon as th main lens for it. I's still waiting for it. I figured if I wanted small, and sharp, I could stick with the Nokton. But the colour shots I have seen from the Biogon f2 made me want it.
I am looking forward to it being my new summicron f2 - my main lens I reach for 90% of the time...
Let's see