Meyer Gorlitz diaplan 3.5/80 to M39 adapter

Meyer Görlitz lenses are famous for their special bokeh.
You can get quite cheap lenses using dia projectors diaplan which behave like trioplans as they share the same "triplet" optical design.

This thing allows using a 3.5/80 diaplan and screw it onto a M39 adaptor.
I use mine on a SONY alpha 6000.