Simplex 6204-60 Gold Tone (060) Mechanical Pushbutton Combination Lock, specially designed to provide exterior access by combination, while allowing free egress at all times by interior knob. This mechanical lock eliminates material and labor expense of battery replacements, and it has a single access code which is programmed via the keypad without removing the lock from the door. This lock has a 2-3/4" inch backset, a 1/2" throw latch, a UL listed floating faceplate, a standard strike plate, and this lock fits wood or metal doors, 1-3/8" to 2-1/4" thick. This lock has a 3-hour UL/ULC fire rating for "A" labeled doors. This lock is constructed of all metal cast front housing, that's force resistant, with a clutch protected exterior thumbturn, a unified interior trim plate, and a fixed interior knob.