Each plant would have had a list of inspectors names and their stamps.
That information seams to have been lost to time, but I would love to find a list like that.
With plants like Hamtramck producing over 3000 cars a day, we can only assume that they had a bunch of inspectors.
Inspection tags seem to be more common on cars built after mid-year in 1970. I have seen some original untouched cars that do not have any.
Most of the tags are small and easily lost too. Some are aluminum, and aluminum and steel in contact with each other causes oxidation. The aluminum usually loses that battle, so some inspection tags are just lost forever...........