A programmable combination lock with keyed lock override is disclosed. The lock employs a stack of rings and dial wheels, with a mechanism for coupling and decoupling the rings and dial wheels. A user can program a custom code by unlocking the combination and rotating the inner and outer dial wheels until the desired code is indicated, and then locking the combination lock to set the code. A keyed lock with a master key couples to the combination lock and can override a combination lock in the locked state. The keyed lock allows multiple keys to lock and unlock the combination lock. In the event that a user loses the master key, the user can use the second key to create a new lock combination to operate the lock, yet render the lost master key inoperable.

A door lock has a body (1) equipped with an internal chamber (2), an external chamber (3) and an interspace containing a mobile unit (4) having an internal cam (40) suitable for receiving and retaining a inner key end, and an external cam (41) adapted to receive and retain an outer key end. A plurality of springs (13) are positioned in the inner chamber (2) in passages parallel to the direction of insertion of the keys; pins (15) of a plurality of pins (15), loaded by respective springs (13) of said plurality of springs (13), are slidable in respective passages extending into the inner chamber (2), in the interspace and in the outer chamber (3) along a direction parallel to the key insertion direction. The external key can be modified to open locks of this type.