What is the MCG mag?

I checked all the usual spots. I did find the remnants of my BS under the back seat but a mouse had already gotten to it. There's a few legible scraps but nothing I could get a code off of. Checked under the speaker shelf, no headliner, tore out the carpet, around the glove box, seat backs, etc. Haven't checked under the buckets yet but I doubt there's a second one in that car.