An attempted robbery was reported in El Rio, California. A burglar spent hours using an acetylene torch to try to cut open a safe in the Leonard Anderson Well Drilling Co. office. When he failed at this, he tried to guess the combination. Finally, he gave up and left. Fred Rush, manager of the company, commented, "He just wouldn't believe the sign. We put it there because we don't know the combination. Now the joke's on us. When the yeggman tried to work the combination he set the lock and now we can't open the safe ourselves."

The sign on the safe (which the burglar ignored) read, "This safe is not locked." It wasn't. [Los Angeles Times - Apr 2, 1960.]