Old texts from the library sometimes still have these perforated markings, ensuring that no one forgets that this particular copy of Morse’s Vibration and Sound, from the International Series in Pure and Applied Physics, isn’t the same one that Grandma’s reading for her book club. They’re kind of charming in their own way, a means of labeling texts that disappeared at some point.
Presumably the librarians could enlighten us on that point, were we to ask nicely.
In the meantime, we’ll just muse over the idea that for a time, some individual had to take every new acquisition and punch a few of these before the first shelving. Some dedicated machine sat on a desk just for this purpose. And when it was a big day, those little punched-out chads probably got everywhere. The spilled glitter of their day.