What is this pin/where does it go?! I have scoured the schematic but can't determine. Had the side plate off in prep for replacing the mainspring, and despite my 'care' this appeared!

Edit: I can't post the pic bc I have no hosting resource. It's about an 'index-finger width' length, and from the wider end steps up to a wider shoulder, then steps down to thinner than the opposite end if that makes sense. The stepped up (widest part) shoulder is about 3/4 up the pin.

See if this works for pic hosting:

IMG-3157 — ImgBB

Sorry, I know that's probably hard to figure out, but i don't see anything else or any place else this may have a twin to reference.

Thanks!