A license plate used to on a police car during filming of James Cameron's 1984 science fiction movie The Terminator.
It is made from plastic to look like a real metal plate. 999 is interestingly the emergency services number in the UK and is seen on a couple of the police cars in the final film. This specific one is unfortunately not seen close up at any point in the finished film.
The piece comes from the private collection of Shay Austin, an Assistant Art Director on the movie who has maintained possession of several props since production wrapped and is accompanied by a letter of provenance from Shay.