Leave the ribs as they are if they ring. Lasted 140 years so far. I would buy a couple sets of odd barrels to practice and learn on. EBay is a good place to find them. That bit of rust might just be a bit of solder that has been there for a century. As to the soldier missing it most likely is just an area on part of the ribs. But if you want to lay ribs use the practice set first. If you screw them up its no big deal.