As far as GM goes,if you're talking about their vintage curb sign,then yes,to a point.
Before 1970,GM allowed each dealership to custom order & design their own signs with a certain mfr. that had pre-designed choices set by GM beforehand.
There was a variety of em to choose from and each rather unique,based on the merchandiser sign catalogs I've had.
Beginning in 1970,GM no longer allowed dealerships to do that,and instead came out with one specific generic "ID sign" sign that all dealerships had to now have displayed on their property.See below..
