This thread brings back some old memories I'd just as soon forget . .

In the old days GM used a single key for all locks and used a 4-year
cycle for key cuts - the keys from say a 1955 GM car would NOT fit a
1956 but would fit a 1959 (I'm talking about just the act of sliding
the key into the lock, not if the key would turn, which is dependent
on the tumbler coding).

 They continued this setup until 1969, when they converted to a 2-key
system (doors & ignition on one key, glove and trunk on a different
key with a different groove cut). In 1972 the key layout was changed
again after GM had a rash of cars being stolen from dealer lots and
storage - the "square" key was ignition only, the "round" key was
doors, glove and trunk.

 I remember that changeover well: I was in college working for a
Buick dealer and changed out the door locks on over 200 cars (that was
NOT a fun job, especially on Electras and Riverias): the door locks
where changed to match the existing trunk/glove locks. Some GM
divisions did that change differently: they changed out the ignition
cylinders, hence some 1972~1974 cars with 3 keys (I think that idea
was to use up existing stocks of door locks with the "square key"
groove cut).

 The 2 key system continued until the late 1990s when GM converted to
the present 2-sided key cut with the PassKey III system and only 1 key
for all locks. If my memory serves me, the "W" body cars where the
first ones converted to the new system.

 Personally I like the 2-key PassKey II system like I have on my 1994
Buick. On the other hand, the 1969-1972 2-key system had the advantage
that one could lock the glove box and trunk, give just the square key
to a parking lot attendent so they could open the doors and start to
car to move it if necessary, but keep the trunk and glove box secure.
With that system you only had to have one spare key in your wallet to
open the car and start it (but it also made those cars easier to
steal).

 When it comes down to it, ANY locking system can be compromised,
even fancy electronic locks (and transponder keys - I've heard reports
that Honda transponder keys are VERY easy to "hack").

Regards,
 Bill Bowen
 Sacramento, CA