Battery

Oh im an idiot. Is the knob the crown? What’s the number wheel for?

i doubt its even noticeable

What sort of watch is it? Generally a toothed crown on the back is for winding and/or setting. Quite a few “backset” watches have been made over the years. I have a few different watches with this feature. It’s not uncomforable. If that’s a quartz watch, I would guess the crown is for setting and numbered bit is a sticker, there to show when the battery was replaced, or when it’s due, and is probably in months. If jt’s not a quartz watch, I have no idea what the numbered sticker would be.