Dual custody systems don’t
have to have a guard key locking the operating. Many systems
have two keys, one directly locking one leg of the shackle and
the other locking the other leg
Figure 7 shows the bottom
of the US Navy lock. Both keys
must be turned together to open
the lock. The lock looks like a
Sargent & Greenleaf but it isn’t.
My research indicates it was
made directly by the Navy.
The Russian Army also had a
similar designed lock. Each key
unlocked a side of the shackle.
Figure 8 is one such lock from
the Cold War Era. It has pin tumbler mechanisms.
Another dual custody lock can
be seen in figure 9. I’m not sure
if this lock is for real. Meaning
it was meant to have two people
present to open it. It was made in
China. The small keyway in the
front blocks the operating from
being inserted from the bottom.
It meets all of the requirements
of a dual custody lock so here it
Change the function
of a lock
A dual key system can per-
form a little known operation. I
am not aware of this need in the
US. The lock in figure 10 has the
operating keyway on the left and
the master key on the right. The
master key can change the func-
master keying to dual custody
depending on which way the key
Many years ago in England,
when the very rich or noble
lived in great homes they had
many servants. The master of
the house had the master key to
everything. However, the servants only had an operating key.
If the master of the house wanted
to lock a servant out he could by
changing the lock to dual custody. I only have one example of
such a lock. The lock was made
by Kaye in Leeds England. This
is a very heavy, massive lock.
This lock has automatic locking.
There must still be a need to
change the function of a lock.
6. Made by the US Navy Very
7. Bottom View of Navy Lock.
8. Russian Dual Custody Padlock.
9. Chinese Dual Custody Lock.
10. Function Changing Padlock.