Looking at the photos, with the exception of the dirt, grime and maybe a little rust, the only two things I see are the trigger guard and rear receiver bridge. The trigger guard appears to be brazed rather than welded. the straightening of the trigger guard is common but I have to admit this is the first one I have seen brazed. The second thing, though it may just be the photo, is the rear receiver bridge does not appear to have been ground (filed, etc.) level or even. While both of these are cosmetic, neither should make the rifle unsafe to shoot. The trigger guard is probably the easier fix but the bridge may be able to be straightened out as well.
The plate in the magazine box is a mystery to me as well. I have never seen that before however, I am sure the previous maker had a good reason or at least thought he did. My best guess would be that it was "needed" to correct a feeding issue.
As always, the rifle can be tested with a spare tire, live round and 25' of paracord from behind a protective barrier. Actually not a bad idea for all rifles that have been "worked on" by unknown person or persons.
By the way, I can see your photos on my phone but not on the actual post here. I have been having the same problem. Something to do with resizing before posting.
