a "signature" like that would have been considered vandalism at the factory and is more likely to have been done after purchase
many trucks got grease pencil marks on the assembly line, for their own reasons, but most didn't - NOT a universal practice nor standard in any way, prolly happened at shift changes to let the next crew know what was happening or if something was incomplete
I've seen trucks with indecipherable marks on the underside of the hood, on the firewall, and on the inner fender - always with something that was easy to wash off, and no doubt meant to be
Bill
