I think you may have missed on the whole concept here. What you are looking at, ie the Mortice or rim locks are just lock hardware. The questions you are asking apply to the Small Format Interchangeable Cores that Best invented many many years ago. Heres a picture
On the left is a 6 pin core, and on the right a 7 pin core
How the Best system works, in a nutshell. Lets say you have a building with 100 offices inside. Each office already has installed a nice mortice lock, but with standard cylinders. Inside each office is a file cabinet. In this building there are display cases that need locks, and a maintinence area that requires a dozen padlocks.
You can buy SFIC compatable padlocks for that maintinence area, display case locks, and mortice cylinders for those 100 doors, and SFIC hardware for those filing cabinets.
You can extensively masterkey the system so that an office manager can open all the office doors with one key, but none of the filing cabinets, or something similar. Now, once the system is in place, all you have to do to change a lock is to insert the control key, turn to the right and pull.
Control key? Yep, that is the strength of this system. The control key operates a second shearline. This shearline controls the smallish looking projection you see on the 7 pin core. This projection keeps the core in the lock If you need more on this I suggest you read more on the Best website.
Pickingwise, these locks generally have no security pins, but tight machining tolerances, and the two possible shearlines to pick to make it rather hard to pick.
