Interesting that the "birthmark" shows up here. These vol2 manuscripts were written around the same time Marx wrote the GothaCritik (1875).
Reminds me, Jan Appel mostly deduced the main points of GothaCritik through a close reading of vol1-3, with quite a few vol2 references. He only read the GothaCritik after his initial studies for the GIK.
Apparently, Gothacritik wasn't a circulating text at the time, despite it creating a bit of a scandal in the late 1890s.