We've actually got one of them in our Force museum.Ballistic Clipboard
The Idea was that you approached the car from the rear, held clipboard in front of you at the window and it reduced the available visible target if the occupant was the one you were looking for.
The mark1 bullet proof tunic would sort the rest.
the morale boosting words of wisdom “ of course if there is a shot into the clipboard you will get away with a broken wrist” , had an effect counter to what the instructor optimistically hoped.
even as a young sprog I thought it sounded like a really shit plan