"What Is This Thing? Several Surgical Instruments Were Found Nearby, But It Might Be Not Related To Them At All"

Answer: "It looks like it was a primitive tool used in the past to assist in birth. Yeouch. A bit of further googling tells me they were used to reduce the size of a babies head if it was too big to deliver, by drainage of the cerebrospinal fluid. Known as destructive delivery. Generally (I hope) for cases where the fetus is already non-living. Frightful."
Pretty sure you are wrong.... the black/blue pages in those are thin. photo looks more like an album.
Better... er... what? That would depend on the specific function of the slide rule. I used these in an engineering drawing office early 70's
#56... That is what is left after removing a metal screen that was painted at one time
came with firearm accesories... Probably a wick for old gun.
But the two things can look more or less identical.