I agree with Bill, but I'd state it like this: your choice, the factory didn't do it - what you see is the way they painted it. An original, untouched truck, which would be a valuable museum piece, would not have filler/sealer in those places.

However, I have seen a 1948 GM Heritage Center truck - the GM restorers did not restore to original appearance. Heck, GM does not even know how to properly describe it: 1948 Chevrolet 3600 Canopy 3/4 Ton Truck.