I made this particular J-3 from 4 different lenses. I was sent a 1952 J-3 with beautiful glass in a focus mount and fixture that was epoxied together, would not come apart. The focus was way off, which explains why the glass was so nice, it had never been used. The lens was cobbled together from various parts, the rear fixture was "not standard" and the black paint was flaking off. I ended up buying a 1962 ZOMZ j-3 from Ebay for the focus mount, using a 1950 optical fixture- wartime alloy (another cobbled together lens), rear optical fixture from a 1953 J-3 (bad glass), and aperture ring from the 1962 ZOMZ. The rear triplet and fixture in the KMZ and German lenses have a different shape from the ZOMZ lenses. The latter have threading up front and a guide ring in the back. It will not screw in deep enough to a KMZ fixture, the KMZ glass will not go into a ZOMZ rear fixture. If you need to reapir a pre-war or wartime Sonnar, you can use parts from a KMZ J-3. The ZOMZ and KMZ J-3's: the front triplet and front element can be interchanged. The rear triplets: different.
ANYWAY! Lots of work and rework, the 1950 Fixture was much too long for the ZOMZ rear that someone put into it in Russia. I bought it 10 years ago, realized much later on that the rear triplet was wrong. I had to file the back-end down trying to make it work, never could. Now it worked out- this lens gives good focus from close-up to infinity as the rear triplet is closer to the front group and the focal length is close to the Leica standard. Not the sharpest J-3 that I have, but the Bokeh is very smooth.
Wide-Open