I've seen a couple lenses in a mount like this: one was done by Cooke and Perkins, had a <CP> marked on it. I suspect "semi-custom" jobs, like what Japan Exposuers does now- but just speculation.
The post-war Carl Zeiss Jena 5cm F1.5 is reformulated from the wartime lens, and has a larger-diameter fixture. In Contax Mount: The rear retaining rings will foul on the RF follower of a Leica camera and prevent proper operation with a Contax to Leica adapter. SO: if you wanted to use it on a Leica 60 years ago, have C+P do a custom mount. Again, speculation.
And Youxin Ye is GREAT to deal with.