Hi:
This is my first post. I've been interested in locks for many decades and have recently been making a (long) web page about locks, not recommended for access by smart phone. Recently I've come up with a theory that there are different types of locks commonly called safe deposit box locks.
Type 1: For example the ones in banks today have two keys where the guard must have his key in the open position when the tenant turns their key. Once open the guard removes his key and leaves. When the tenant locks the box it also resets the guard side of the lock.
Type 2: In a jewelry vault there are boxes protected by locks with more security than the Type 1 locks above. These may be combination locks or key locks but there's no need for the guard key.
Type 3: These are locks at the back of (floor or high security) safes that need a long key (where do people carry the long key? not on a key ring).
Type 4: These are the mystery locks I have. One is a Yale & Towne with provision for 4 tenant and 4 guard wafers. It seems way too big and heavy to be used in the Type 1 application and has a single nose with provision for two keys that must be used sequentially. Like two people must be there to open the door, so very high security. The patent calls it a safe deposit box lock.
See:
http://www.prc68.com/I/Locks.html#Yale_8-Lever_A very similar Yale lock with provision for 5 tenant and 5 guard wafers and more in line with the size and weight of Type 1 locks, but the tenant key is 0.080" think and has grooves (is warded), not a flat key like the guard key. Why the warded tenant key?
http://www.prc68.com/I/Locks.html#Yale_10-LeverPS You can click on a thumbnail photo or patent and see a larger image.
PPS I have a small number of YouTube lock videos:
https://www.youtube.com/playlist?list=PL-b7wcJ1xQUAQ9FYmMUxqe-lDlBQEzLVgHave Fun,
Brooke
