This material was excertpted from the
Mark Bates book titled Modern Safe
Locks. The book covers combination
operating and changing procedures
for virtually every combination lock
both mechanical and electronic, that
you will ever encounter on a daily
basis. Modern Safe Locks is available
for purchase through The National
MOSLER CDK 120
MODEL: CDK 120
DESCRIPTION: Three wheel, key changeable combination safe lock. The dial
is numbered 1 through 99. Regular change.
RATINGS: UL Group 2
PROCEDURES: a. 4XL to 50
b. 3XR to 25
c. 2XL to 50
d. Turn dial right to stop (about 78)
TO LOCK: Turn dial left 4 times.
FORBIDDEN ZONE: 90 to 10.
CHANGING WITH THE SAFE DOOR OPEN…
PROCEDURE: a. Add 10 numbers to each number of the existing
combination (50-25-50 becomes 60-35-60).
b. Dial this combination to the opening index (steps a through
c under “Opening Procedure”).
c. Insert the change key and turn it 1/2 turn left.
d. Select new combination, then add 10 numbers to each
number of it.
e. Dial this new combination (with the 10 added numbers) to
the opening index (steps a through c under “Opening
f. Turn the change key 1/2 turn right and remove it.
g. Test the new combination (less those 10 added numbers)
at the opening index (steps a through d under “Opening