Brass-colored ignition key

My RMW came with a blank-looking brass-colored ignition key without the VATS resistor. Has a 4 stamped on it. In the knockout hole is a tag with a code- I assume this is the key from the production line or something, but what's it for?

Its the key for a replacement ignition switch. That key is supposed to be so you can have a vats blank copied for the ignition. I can only assume the car is running and if so the vats on your wagon has been bypassed/disabled. I know because i just replaced mine and bypassed vats a few weeks ago, been using the brass key ever since.

Your VATS module requires a #4 key. The locksmith stamped the number into the plain key that comes with the switch so that if a new key is ever needed the next locksmith will know what key blank to use.

New AC Delco ignition switch assembles come with the key blank with no VATS pellet, to use as a guide to cut the new VATS key at the dealer. There must be a reason why..

The reason is the fact that there are 15 different resistance values and only one key cylinder.

Right. I forgot that. Haha

Thanks- that does explain it. Found pictures of the Delco replacement and that's exactly the key I have. Obviously replacing the cylinder has nothing to do with VATS, my VATS is enabled and works as expected- I tried starting the car with the brass key and it doesn't work.