Chevrolet 1994 Blazer Owner's Manual page 58

The oval-shaped key
is for the doors and all
other locks.
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 these plugs.
I
NOTICE:
Your vehicle has a number of new features that can help prevent
theft. But you can have a lot of trouble getting into your vehicle
if you ever lock your keys inside. You may even have to damage
your vehicle to get in. So be sure you have extra keys.
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