Really, I did not know that? Hmmmm. Strange how some boxers would do that. Someone should start a thread on boxers who switched from their natural stance (assuming it hasn't been done before). Obviously Cooney was, Frazier too? I have a feeling Barry Mcguigan was left handed.
Watt simply found he was more comfortable boxing out of the southpaw stance, so he developed that way.
Another good one not mentioned yet was the mw version of Nunn. Pre-Roldan/Barkley of course. Pre-title and Tate versions guy. He only had it for about 2-3 years tops, but he moved his legs and flicked that jab out there and really controlled the real estate in the ring with it. And early on, it was almost impossible to counter it. But as soon as he lost it, he did not have the other tools to compensate, unlike a Camacho type guy.
Marvin Hagler. He had a great jab, and then when his opponent was getting tired he would leap in and use it to wear him out more.
He sure used that jab in helping him out-think and out finesse Howard Davis...a very impressive performance to me at the time.