Here's a quickie of the change sidebar, the locking bar wafers, slug, and case.
I'm not sure whether these actually need a change key! The way I see it is you use the lock normally as you would with the key you have, but should you want to change it you insert the current key in.... turn 180 degrees, remove the key, insert the new one, then carry on using that as normal.
This one is apart anyway, which gives me a better idea on how to open the other 3 (no keys).
Cutaway tomorrow hopefully! Got some insane cuts lined up for this baby