I am glad to see the Pentax 67 lens came out of the closet. I have the 75mm shift, 105mm F2.4, 160mm F2.8, and te 400mm F4 lens. I had the 55mm which I sold it and regret. How can you tell which 55mm F4 version looks like and is a better performer? I will attempt to make an adapter and give these lens a chance to see lights again.
Over the years Leica has offered more choices to one of the most popular focal length, “normal” 50mm. They all have their unique contribution to the functions from optic to ergonomic; a difficult choice to pick. However if I had to pick one or two, my choice would be the Noctilux F1 for black and white film and the 0.95/50 for the digital camera.