It's said that Jeffries used this technique, anyone earlier than him? I've read lots of references to NP Jack Dempsey as being "two handed" but i've never read that he switch-hit...
That IS early. That's early than I would have anticipated. I guess there is probably no way to know, but I wonder what his history was? Was he trained as an othrodox fighter, as would sometimes be the case? Or had that type of southpaw naziism not descended on the sport yet? Do you know any details of his fighting style? Was he a bit flash?
He was regarded as a scientific fighter by the standards of the day and would often frustrate oponents.