​2.5-inch solid plastic black spindle/key/plug with notches in the junk drawer

I moved a few months ago and found this in my junk drawer. Unfortunately, I can’t recall what it’s from. I also am unable to remember if it was in the junk drawer at my previous apartment or if it found its way there during the packing/unpacking process.

I’ve included images with measurements. The entire piece is about 2.5″ long. The bottom (~7/8″) is wider than the top (~3/4″).

Reverse image searches mostly suggest it’s a film spool, but I’m not convinced.