Chatwood's changeable key lock. The advantage of fitting a changeable lock to a safe is obvious, because if a key is lost or stolen,or copied, the lock can be immediately changed to suit a different key. Five keys were normally supplied with each lock. The levers which have no gatings in their edge but have teeth. mesh with teeth on wheels mounted on a spindle.When the teeth on the spindle are moved away a new key can be introduced turned as to lock, remeshed and the lock now only opens to the new key pattern. Patent date 1886.