It's a padlock with a code. The manufacturer makes the padlock with a specially made pin, so you can lock your front gate, and feel secure.

eMudhra sent you a padlock that had the code "4815" promising no one has ever used it or would be able to guess it, but all anyone really needed to try to get in is set the first number to "4" and ignore the rest.

It's not entirely accurate, but its accurate enough for them to get.