picking. It completely destroys
the idea of paracentric keyways
which were the only deterrent to
The idea of one tumbler having two different lengths was
popular in the late 19th Century.
Several Large US lock companies
each had their own design, but
all were virtually the same. Specifically, Norwalk, Sargent and
Chicago Lock Companies all had
the same idea. Their locks were
true pin tumbler mechanisms but
each pin had a right and left side.
This approach allowed a common
master key to use one side and
the operating keys the use the
The problem was to prevent
the pins from rotating. Sargent
actually used square pins (figure
Figure 19 shows a pin with two
left and right key bittings.
Figure 20 is a close up of the
Sargent plug. Carefully note
the first pin. It is clearly square
and has two different cuts. This
method of master keying was
used be Sargent around the
turn of the last century. Many of
you probably have this padlock
and don’t realize the interesting
mechanism it has, (figure 21).
Chicago Hardware Company
also used the concept of the same
plug containing two different key-
ways for their expanded master
keying (figure 22).
Norwalk Lock Company used
the duel keyway plug at about the
same time (figure 23).
An interesting side point
here; Note that the mortise
cylinders of the late 1890’s were
not standardized. Each lock
manufacturing company had their
own special diameter. Nothing
was standardized as it is today.
Yale must have set the standard,
because the standard size we use
today, 1 3/32”, was started by
Yale. By the 1900’s most lock companies were standardized to Yale’s
Dudley Lock Co. actually has
master keyed padlocks using the
same left and right keyway concept. However, Dudley, because
their lock can be considered high
security, uses four different bitting positions.
The lock in figure 24 was
Continued on page 32
16. Left and Right Keys Using the
17. End View of Plug Note the
Left and Right Lands.
18. Sargent Square Master Key
19. Pin Removed Showing Two
20. Note the First Pin. The Right
Side needs a higher Cut than the
21. Square Pins are Most Likely
to be Found in this Case Style.
22. Chicago Cylinder Using Left
and Right Keyways (Pat. 1892).
23. Norwalk Cylinder With Left
and Right Key Blanks.
24. Dudley Early High Security