When drink driving was considered unwise but legal, this simple mechanical device, sited in pubs and clubs, allowed you to gauge your inebriation.
Insert a coin, which is held by a gate at the top, and press the spring-loaded green button, which is then held in place by a rubber sucker. At this point a battery contact is made to illuminate a bulb, the previous coin played drops to the cash box and your coin drops below the gate to rest on a pin connected to the button mechanism. You then wait until the sucker loses its grip, puts out the lamp, rings a bell and releases the coin. The coin falls vertically and you have to press the red button as fast as you can. The coin is stopped dead as one side of the channel closes against it. Your reaction time is measured by how far the coin drops against a scale, indicating your stopping distance when travelling at 30 mph, with comments about your fitness to drive. If you are fast enough (within 21 feet) you get your coin back. Patent GB786414