This is an interesting topic. My only thought on this is that the markings were there to keep track of certain units, like firewall stampings. Maybe the shop superintendent wanted to keep track of the number of firewall stampings made so that when a certain number of them had been made available to be sent to the assembly line, the press operator could switch the dies in the press to produce something else that was in short supply, say, like inner fenders. I dunno', Jacques
