Marginalia-criminal?

Liber I of Casavboni, Animadversionvm. Lvgdvni 1600, full of blue pencil margin markings. What a horrible sight. Seemingly meaningless dashes and crosses. Well of course not really meaningless as someone took the trouble to place them and the fact that they are only placed in Liber I must mean something. When were the markings placed? They do not seem comtemporary.
It seems too much honor to even make pictures of them, but of course I did for completeness.

The circle on the page above particularly hideous in its supposed uselessness. Maybe a child took it's chance?

I felt a little like this:

Casavboni, Animadversionvm. Lvgdvni: Antonium de Harsy, 1600. p. 1
U.v.A. call number OTM: 63-847

so to cheer myself up also took some pictures of a few of the numerous intricately decorated initials, head and tailpieces.