1975 buick lesabre important question

we father and i just recently bought a 75 lesabre convertable and found a plaque in the middle of the dash that said 1975 buick lesabre end of production and also had classic on it. Now is this something that was done on the line or did someone go to the store and pick it up and put it on there. Any suggestions? If you could help me out i would greatly appreciate it. thanks

Iv'e seen one like that, too. I think they are put on @ the factory.