Thanks all. I'm not a Contax guy, obviously, but the lens that I fell into is a 1934 fernobjectiv 50cm f8 with the flektoskop viewer. Not a collector and not my thing, but I'd like to have a play before I send it along where it likely will grace someone's collection.
You will find a Flektoscop very awkward to work with, but the up side is that your lens-reflex combo is much coveted by Contax collectors. Good luck with your find.