I should perhaps add that the top cornet players were individuals, not band members, who spent their time touring, teaching, competing, writing method books, and very often played as guest soloists. But for the most part, they were touring soloists. They had fans and followings, and their followers tried to get their hands on the same music and the same instruments.
In terms of performance practice, it has to be said that the individual players driving the scene did not want to sound just like everyone else. If you were to go looking for that "classic cornet sound" amongst the top players during the heyday of the cornet, you would be disappointed, because the players themselves were all trying to distinguish themselves from one another, mostly by specialising at something- tonguing, change of register, playing lyrically, playing loudly, playing high, playing extremely fast, exploring various styles.
Perhaps you guys haven't seen the equipment they were using back then? You should see old collections of cornet mouthpieces. Huge, tiny, extremely deep, extremely shallow, V-cup, parabolic cup, C cup, thin rim, round rim (an extreme chop-killer), wide rim, extremely wide rim, flat rim, you name it.