Kind of seems weird the guy was selling "miscellaneous" repop sign for $350 & "Ford" signs for $150. That seems backwards too?
Only thing I think is very important to add to this discussion is that auction houses are NOT authenticators. They kind of have their "own" reasons to stay neutral...
Ebay is probably the best example of that, I'd say 85-90% of the signs are "fantasy" / NOT authentic.