If I'm not mistaken the first word in this thread actually has two marks. In the close up showing the S there is also, hidden in the second fuller a "fly mark" visible just above.
Both seem to have been pretty popular on schiavona, I'm not sure there's a whole lot more to add other than the fact they they are typical markings and what I would expect to see on a blade of this type in these mounts.
Great sword by the way!