...I used to have one of these signs...and there was a mark left where something was attached to the face of the sign...you could see the difference in the porcelain face of the 'keyhole' sign, where it had been covered by the name plate, and hard water stains (not rust) that indicate the edge of something that had been bolted to the face of the sign...the size, shape and location of that 'ghost' image leads me to believe that there was originally a name plate attached there...not 'bolted on afterwards', but at the same time the sign was affixed to the truck door...seems to me that those two bottom holes would be lower, more 'centered' along the left and right sides, if they didn't serve two purposes: attaching the personalized name plate, as well as the bottom portion of the sign to the door...
...but, hey - Texaco's not my thing like Gulf is, so you might be right...
