Wouldn't the license plate rattle too?
Looks like it may be a California dealer plate.
If it is, that would explain why it is temporarily mounted with a string or wire around the radiator neck.
Dan: This is as old as the hills but it is said the following is true:
You can only tell the difference between a Ford and a rattle snake because you can count the rattles on the rattle snake but not the Ford! I know you are say how stupid is that but it is true.