In the Zombie map "Kino Der Toten", there is a teleporter in front of the curtain on stage. When you use this teleporter, you get sent to the room that has the Pack-a-Punch machine and a window. If you wait about a minute you'll be teleported again to one of several secret rooms. Inside the secret room that contains the presidential seal and a projector, there is a desk. On the desk there is an old roll of film which you can pick up (be warned you will not be prompted to pick it up, you just can).