Chevrolet 2000 C-Series Owner's Manual page 47

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The square head key
is for the ignition
switch only.
If you have the optional one
will operate all locks, including the ignition switch.
When a new vehicle is delivered, the dealer removes the
plugs from the keys and gives them to the first owner.
Each plug has a code on it that tells your dealer or a
qualified locksmith how to make extra keys. Keep the
plugs in a safe place. If you lose your keys, you'll be
able to have new ones made easily using this code.
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The oval head key is for
the doors.
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key system, the oval key
2-3