Chevrolet 1993 Astro Passenger Owner's Manual page 60

Features & Controls
L
K5316
The door keys are for the doors and all other locks.
K1298
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.