Interesting point about MTOs and T2 mounts. So far I tried M42 and Nikon T2 and it works.
I just measured thickness of T2 adapters I have here and:
M42 is 9.4mm, Nikon is 8.6mm and one with out marking is 11.4mm thick (Minolta MD?? Konica??)
Don't forget that MTOs also have focusing past infinity mark so you can try simple thin Nikon to m42 adapter with out correction lens, (one with lens are mostly horrible) and check how far away you can focus with it.
Pentex makes an adaptor for 42mm to K mounts, but not all bodies, most of the auto foucs, will not meter and the shutter locks up. SF1 and SF1N will meter in manual and A mode and are inexpensive . Most manual focus k bodies work as well. Chinon's, also sold under GAF, CE 3 will provide aperture priorty metering and can be used with a motor winder. Spots with working meters are great cameras and will work your lens.
Just stare at them, for now. When time permits I will try them out, but with all this snow and weather forecasts I don't see it happening for another couple of weeks. Gorbas suggested I should try to mount them on my Nikons, which I will look into as I would rather test them on something I am comfortable with.
And no, I haven't checked Fotodiox adapters, but now I will.
There was a west-german company named Beroflex importing GDR cameras and lenses. Berogon most likely is their tradename.
The west-german mail-order company Quelle used the brandname Revue for the optical products they sold. Revuenon most likely is their tradename. They imported and re-branded, amongst others, soviet cameras and lenses.