Dear Wes,
thank you for your reply.
Actually, my grandfather owned a Contax-I first, then the II, bought late in 1937 and, after the war, a IIa/IIIa. I also have a III, belonged to him, but I don't know if purchased after the hostilities. One thing is sure, in 1943, he received a Sonnar 50/1,5 (Red "T") as a present from his brother, who was a journalist in a German newspaper.
Back to the Tenax, searching through some of his surviving papers and family memories via-my mother, I think he bought it in 1940. I've always seen it, mounted with that Sonnar.
He taught me the "how-to" in photography with his Contax-II (a camera I still have and sometimes use, along with other, related, Zeiss equipment), but I remeber that he -especially while hiking or climbing mountains- took the Tenax, or the folding Contessa with him.
Best wishes,
Enzo (E.L.)