How skilled were these fighters? Broughton and Mendoza are described as technical, yet I'm not entirely sure what their punches were. Dutch Sam apparently invented the uppercut, so what else were they missing during the Broughton era? Are there any books on their styles?
Well Broughtons rules brought a bit of order to the pugilism, so no hitting a downed man etc, plus he had a focus of placing his punches rather than winging in blows, so i guess that could bring about him being described as technical.
Some rules existed long before Broughton, as noted by several foreigners who visited England in late 17th or early 18th centuries, in their diaries. And we are talking about common people, who weren't participating in prize fights, they already understood some things they shouldn't do if they chose boxing to decide some conflict.