I wonder what happened to them also. I may have seen one other since I sold the main bunch of them in one deal.
Yes that would be nail holes. They drilled a small hole and then drove a 16D spike through it...found some broken drill bits in some of the holes. Thats why it flares out like a bullet hole. The signs overlapped so the mounting holes lined up...the building was painted after it was put up...that may make it look like a frame was attached?
I think nail holes are more desireable than bullet holes.
Jim