Foreign Two Key Locks
Europe has also used the
concept of two keys for expanded
master keying. Without going
into detail I wish to share just a
few of the more common European two keyway locks. The lock
in figure 1 is a large English two
keyway lock. The keyway on the
right is the master and the one
on the left is the operating. This
lock was made by Gibbons.
The lock in figure 2 is also
a two keyway lock but I am
not sure where it was made. It
also has an operating key and
a master. Europe seems to use
two keyway master keying much
more than the US.
Both of these locks have a
lever mechanism very similar
to the Yale Duplex in figure 6 in
A very interesting two keyway
padlock is shown in figure 3. This
lock could be German because
of the type of pin tumbler mechanism the two plugs have. I have
only seen this crossed, four way
type pin tumbler mechanism in
The discussion, so far, has
been about master keying using
two different keyways. The next
use of two keyed locks is about
increasing security by having two
people with different keys open
the same lock at the same time.
These locks are usually referred
to as “Dual Custody”. Another
term that is used is “Safe Deposit
Function” (like a safe deposit box
Because it isn’t physically
practical to have a mortise cylin-
der with dual custody this func-
tion is most commonly found in
The first padlock one usually
thinks of is the Yale Bicentric.
Yale made this lock with various functions. The dual custody
Bicentric usually has its two
keyholes marked “GUARD” and
“OPERATING”. The guard key
has the same function as the
bank key in a safe deposit system. It can’t open the lock alone,
it also needs the operating key
Also note in figure 4, the
guard key has a restricted keyway (reverse of the operating).
This is done to make duplication
more difficult. Yale did make
one experimental Dual custody
mortise cylinder in the 1920’s.
Figure 5 shows a short guard key
that locks out the larger operating key.
I have never seen this cylinder
in production. They probably did
not make it.
1. An English Two Keyway lock.
2. A European Two Keyway Pad-
3. A German Two Keyway Pad-
4. Dual Custody Bicentric.
5. Note the Plug is Locked
out at 20°.