As for the rib, Classic Arms in Tennessee did some work to the rib - which I believe has been replaced. I called them describing the work and they thought that it was welded material for reinforcement. I've been told they do quality work on vintage guns so I'm not questioning it - It's a gun I plan on using in the field anyway.
I enlarged the image of the "repair" on the bottom rib and it doesn't resemble any sort of welding I've ever seen. It looks more like a soldering job that didn't go too well, and that some peening of the solder was done. Hard to tell, but I'm guessing the entire short section of rib behind the forend loop may have been missing, and someone decided to just fill the gap with solder. I'm betting that if you were to forward that image to Classic Arms, they likely would not want to take credit for it.
It may not affect anything, and it is hidden under the forend... but I'd want to repair it properly, and check the integrity of the solder joint on the forend loop. It would really suck to be out hunting, and have the forend loop pop loose, and possibly lose it and the forend. Finding replacements would be near impossible. You may find the current Thread on rib relaying interesting.
I'm glad a new guy like you was able to post images here without any apparent problem. Some guys who have been here for years find it to be a daunting or impossible task. A few more pics of the complete gun might make it easier to get an accurate valuation.
