Lockhart comments to Baxter "If only car owners would cover up the number on their lock with a bit of tape or something, it would help". At that time, in the early 1960s, it was common practice for car manufacturers to stamp the key number on the ignition keyhole to make it easier for owners to order a spare key, but observant car thieves could read the number (as Rye mentions to Morton) and buy their own key. Also, the number of different key combinations was far less than nowadays, so a key for one car would probably open some others of the same make and model.