doublegunbum, are the two studs you referring to, the two lugs that are on both sides of the barrel lug? If they are, those are present on the 1896/1897 or Model D grade (hammer gun) and the Model C grade(box lock gun) along with the B grade and higher Bakers. The Leader and it's same class of brothers(Special,Black Beauty) did not have these lugs. You can obviously put the Leader style barrels on a two lugged gun, but not the other way around. It is not terribly uncommon to see a Batavia Leader, Special or Black Beauty barrels(no side lugs) on a "graded" (lugged) guns.

Robert,could you post those patent drawings?