Pre-Worn Keypad Lock

I was recently at an airport, and while waiting I noticed a "staff- only" type door with a numerical keypad lock. A closer look at the lock showed that it was almost entirely wear-free except for the "1" and "9" keys. Furthermore, there was clearly a lot more wear on the "1". From this, it's not difficult to dramatically cut the number of possible combinations that open the lock. Add in human tendencies such as laziness, and I thought that there was a 50% chance the combination was 1119. I wandered over and tried. I was right, and illicit access to a cleaning closet was mine!

Such factors defeat the purpose of the lock, which is, presumably, to deny the public access to mop buckets. So what can we do?

Lock manufacturers can recommend that customers change the combination frequently, but it won't happen. So, after the lock is made, it's put through an additional process that randomly distresses 2-3 keys. Then, in service, it will be a lot more difficult to determine from wear patterns what the lock combination is.