Could you tell what caused all that damage? It looks like it was stored in a gravel pit and dragged behind a truck down the gravel road.
We speculated about that some in the original thread after I bought it but never came to a concensus. Some suggested blood, others the foam lining of a gun storage case. It didn't look nearly as bad in real life as you described above - as I said, "It looks great everywhere, except where it looks horrible."
I think it was some kind of chemical spray due to the very fine nature of the damage on the cylinder, visible in the closeup. The area where the marks were individual, it was if a very fine mist of acid or something had landed on the gun and just barely gotten through the bluing. In the closeup you can see some ultra-tiny pits in the bare areas, finer than the tip of a needle. I could only see the pits with my eye by wearing an Optivisor with a 3 diopter lens, and reading glasses under that. I think if the whole gun had been washed in this substance it would just come out "in the white".
Other areas show a little more conventional corrosion, like at the very bottom front corner of the frame, and the pivot of the crane. But these weren't very deep either and almost completely buffed out. There's one spot just above the "S" in MADE IN U.S.A that's still barely visible, but that's about it.
I'm still baffled by the logo movement on the sideplate. If they buffed out the original and restamped it, there is absolutely no trace of the original logo, and the sideplate hardly needed any refinishing anyway - just enough to make it match. If they put on a new sideplate, the fitting seems flawless. (I have no idea how they match those curves between frame and sideplate anyway - it seems impossible but obviously they do it on a daily basis.)