How about taking a video of the damage and posting a link...
Sandblasting incorrectly (I'm sure this is the first time in 40 years he's F'd up...
) will stretch the metal and will require some strategic shrinking to remove said damage. In many cases it happened as someone was cleaning off an inside brace and at the edge of the brace the media struck the outer skin (but not under the brace) This abrupt "cut line" of media blast vs. no media blast is normally where you'll see such damage.
