It's on a color-matched embossed metal decal in your hood. It is on the front where the hood latches to the grill. It'll have a whole bunch of numbers which correspond to your model, engine, color, and options.

I deciphered mine one time and they built it right! You'll have to search the web as there are a few sites which have all the codes.

Good luck and happy hunting.

(btw this was on my 500E as it may be different on others?)