They are human welded. I thought that but I have never seen square holes at the end of welds before. Its not like a fish eye, it is actually outside the weld up to a 1/2" away so far.
I am looking at some enclosures and some of the welds have square to rectangular holes at the ends of the welds. Some appear to go all the way through and others are just into the material rather deep. The square hole is just outside of the weld. Its 1/8" plate and D1.1 does not seem to cover...
