This is just a little bit old, but there are still plenty of cars that sport the numbered keypads to unlock the driver’s side door. There are really only 5 keys here, and thinking outside the box, one can quickly test that this is just a password entry, but there is no end bit or anything. It just sits and listens and waits for the proper combination no matter what preceeded it or followed it. Turns out, it only takes 3129 keypresses max to get the door to open. The article states this takes about 20 minutes. Just imagine reciting the cheat sheet into a recorder like an ipod and then just listening to the sequence as you key it in.
The more I think about it, the more it makes sense that this whole idea didn’t last very long and not all that many cars used it or still use it.