Weird tag

Fairly sure thats an inspection tag. The assembly line workers would mark it as their process was completed.

I think it should have been removed before delivery, but for whatever reason, wasn't.

Right you are. This was a inspection tag that was attached under the fender tag. At different areas along the assembly line inspectors checked to ensure that different systems were correct. If the car passed what he was checking for, a mark was stamped into the tag to confirm.