Funny tag on fender- what is it?

Here are pics of my collection. I think this thread is on the right track. These extra tags are not rare but are not all that common. I think that them not being common and not knowing what they meant is what lead me to collect them. Have always felt that they were inspection tags, but then why did these cars get them and not the others? You can see two examples were a car got a "double tag". The other tags are inconsistent in the material, size and info contained. I'm hoping that someone here worked on the line and can help us.