Random – You will receive 2 key copies with the lock. The lock and key combinations are completely random
Series – Different key systems. Each letter represents a different key system that could be implemented in a different buildings or different wings of the same building
Number – Individual key codes.
For example you could purchase a keyed entry lock with a key code of A-001. The utility closet could be A-002. If you ever need to replace a lock or order keys you can do so online.