So in the last pic, the part with rivet, lets call it the "hook". It is touching a bar just to the right. We'll call it the "drum catch". When the drum in the center w the spring rotates the "drum catch" locks into the ratchets on the drum. When it does that the "drum catch" moves down slightly. Then the "hook", which is the lock mechanism, can move over to prevent the "drum catch" from unlatching. I would make you some pictures but all my locks are at the platers. I just recently studied this mechanism as I went through mine and was working on refurbishment

13 hours ago, Patcon said:

So in the last pic, the part with rivet, let’s call it the "hook". It is touching a bar just to the right. We'll call it the "drum catch". When the drum in the center w the spring rotates the "drum catch" locks into the ratchets on the drum. When it does that the "drum catch" moves down slightly. Then the "hook", which is the lock mechanism, can move over to prevent the "drum catch" from unlatching. I would make you some pictures but all my locks are at the platers. I just recently studied this mechanism as I went through mine and was working on refurbishment

This makes sense. This is likely the reason the previous owner had riveted it in place so that it wouldn’t accidentally lock as there isn’t a key hole nor rod knob.

Why not contact “junkyard Jenny” She probably has what you need to replace your existing mechanism. Sounds like you might need both sides. Good people.