The adapter was produced by grafting a Kiev helical onto a cheap M39 to E-mount adapter. The Kiev helical had been machined to fit in the M39 adapter and had been glued in place with what I assume is epoxy. I was curious about how well the adapter worked, so tried it out on a bunch of Contax RF lenses, including 3 pre-WW2 CZJ 5cm lenses, a Zeiss-Opton 50mm/2 and a Carl Zeiss 50mm/1.5 using the wide open, one meter test that Sonnar Brian uses. Much to my surprise, the adapter was dead-on using the above 5 lenses, they all hit precisely on the one meter mark. It also worked well when focused on my measured 5-meter indoor test area. Ironically, when I tried the 1950 ZK on the adapter, the lens front-focused about 15mm, which suggests that the shim on the ZK lens is a bit too thick. While this adapter is not an elegant piece of machining like my Amedeo Contax to E-mount adapter, it appears to work really well. The Ukrainian guy that cobbled this adapter together did a good job. Similar to the woodworker's truism about "you can never have too many clamps", one can never have too many E-mount adapters