I understand what you mean fred, but look at vintage cars, there is not one out there that hasnt been restored, also it depends how deep your pockets are and how fussy you may be, i know for a fact if my lass was into enamels i would be skint, as she will not have ANYTHING if there is as much as a scratch on it!
also, what if the sign was one of a kind, and needed resto to show it off truly?