Advice on broken ratchet wheel tooth

The ratchet wheel screw is a pee poor replacement. A broken tooth in the ratchet wheel could well result in other broken winding wheel teeth as well. Loose case clamp screw May be a simple cure, or a symptom of yet another problem. Beneath the rim of the ratchet wheel you can evidence that the ratchet wheel has been rubbing on the barrel bridge to the point that the nickel plating has worn through to the brass. Worn out mainspring arbor bearings, and possible a loose, floppy mainspring barrel. And it would appear that the case back may have been rubbing on the bridge over the train wheels. You don’t want this lemon!