A top-notch lens, and a better performer than my 50mm Summicron or Summilux. I bought the example I use because much of the black paint had worn off, leaving the brass exposed. It was a good match for my brassy, black-paint M4.
Because of the ugly appearance of the lens, and the dirt cheap price, I didn't expect it would perform very well. I was quite wrong, it is an incredible lens.