I thought I would post this since I had difficulty finding information about this lens and how it performs on a leica screwmount body. As a disclaimer, my lens appears to be at least post 1947 when the lenses started being coated and having a standard aperture progression (3.5 - 4- 5.6 - 8 -11 - 16), so perhaps there is some standardization that was applied to it to function properly on Leica bodies. A lot of the information that I have read about these lenses is that their flange distance was slightly longer on FED bodies than on Leica bodies, even though they have the same thread pitch and diameter, leading to backfocus. If this problem exists on this lens, it is not visible, at least not in my sample. So essnetially it looks like getting one of these in decent shape and a later edition of even the early Industar-10 can give very good results and work fully on a leica body for much less than an Elmar. I do have to say although it feels nice and has about the same weight as the real Elmar, the focus tab dosent always lock, the aperture may need cleaning to move properly, and the distance scale is likely inaccurate. I cleaned out this lens and relubricated and adjusted everything, so its in great shape, and luckily has a multicoating and does pretty decent with color. Attached are two pictures I took with this lens at f3.5 to check to make sure the focus was accurate and it is. The one with the sign is about 10-12 feet away, the newspaper box is about 4-5 feet away. In conclusion, it may be worth it to try this lens if you are simply looking for a small collapsible 50 to put on a screwmount that you can slide into your back pocket for a good price!