The hole in the lock cover, that also runs through each wheel & into the lock casing are for the change key, which allows the combination of the lock to be changed.
The lock is dialled to align the holes in the wheels with the hole in the lock cover. Most key change locks have a second index marked on the dial ring & alignment of the change key holes in the wheels with each other & the change key hole in the lock’s cover is achieved by dialling the combination using this second index mark.
A change key (specific to the model of lock) is inserted & turned through 90 degrees. This disengages the outer section of each wheel from its inner section. A new combination is then dialled, again to the change key index.
Then the change key is turned back through 90 degrees in the opposite direction, which re engages the inner and outer sections of each wheel, and the change key is removed.
When performing this on a safe lock that is in use, the new combination should be tested several times, before locking the safe! Many lockouts are caused by failing to verify that a new combination works.
I am unsure, but I think the brass plate you ask about seems to play a role in the operation of the change key, perhaps it limits the travel of the change key when it is turned.
I do not know if it is possible to repair or replace the wheel post - I’m sure other more experienced members can advise you regarding this.
Hope this helps,
…Mark
