Will give this topic a one time bump since I'd really be interested to know. Nota bene: it concerns Dr. Joachim Obwegeser (not his uncle Dr. Hugo Obwegeser, I assume he retired).
Here is the best answer for your question that I can put together:
Joachim was taught and learned how to do the full spectrum of orthognathic jaw surgeries from his pioneer uncle, Hugo, at Hugo's clinic in Zurich. After Hugo retired, Joachim continued as the head of his Uncle's orthognathic surgical practice at that clinic for a number of years. During that time, Joachim was the clinical instructor in orthognathic jaw surgery for a number of European max/fac dentists who have done fellowships at his clinic and for at least one American M.D. surgeon who traveled there and secured one of those rare training slots.
Given that background, one would reasonably believe that Joachim is at the top or among the top tier of European orthognathic surgeons in terms of training, experience, and capabilities.
