In my mid 1970’s elementary school, we called these acorn clips. Apparently, this was an extremely isolated phenomenon as no one I’ve ever met has ever heard of these brass paper fasteners being referred to by that name. Googling “Acorn clips” and “brass acorn clips” results in zero images of this product but I swear I’m not making this up. I’m not even sure I can explain why these may have been called acorn clips- save for the fact that they look a little bit like the stem from a pair of acorns.
Do they still even make these? (They do) I got these from one of my friends who found a box at a thrift shop.
According to Wiki, they are also known as “split pins” and are an industry standard in binding screenplays in film industries across the globe.
Here’s a magic trick using a brass paper fastener.