To be brutal there was never a point when they became DIN adapable the Conshelf XIV always had a thread on the back end for the A clamp to screw onto and was there all along.
After I posted this question, I did some more research and I believe, answered my own question. For those interested, here we go.
The Conshelf XI had the smaller yoke, it was the the Conshelf XII that saw the introduction of the "heavy yoke" but it did not thread down on the body. Same yoke used on the heavy yoke RAM (discontinued in 1975). It was sometime after that, or the introduction of the Supreme, that we see the threaded body that the yoke screwed down on. And it was that model, and the Conshelf XIV that we see the DIN adapter option, you unthread the yoke and thread on the DIN.
Let me know if anyone out there had a different idea?
I found this on vintage scuba forum:
1965-1969 the Conshelf VI regulator was in the catalog
1970-1971 Conshelf XI appears
1972-1976 Conshelf XII is now marketed
1976 Conshelf Supreme
1977-1982 Conshelf XIV and Supreme
1983-1984 Conshelf 20, Conshelf 20 Supreme, Conshelf XIV, and Conshelf Supreme listed
1985 Conshelf SE Supreme, Conshelf 20, and Conshelf 20 Supreme