Quote Originally Posted by Loose Gravel
It is a focuser and is threaded on the camera end. I don't know what Leica threads look like. The threads are male and about 1 19/32" OD. That's about 40mm. Could this be the Leica 39mm thread?
Sure sounds like it! You may find that the maker tried so hard to copy the Leica 135 mm lens (called a Hektor) that he also made the lens head capable of being unscrewed. If so, the lens could be used for many other things (the lens head of the Hektor when unscrewed covered at least 4x5").