Build sheet question

[zmanrc]

Friend just picked up a '79 Z28. White, blue stripes and interior. Going to be a nice car.
We found most of the build sheet under the back seat. Mice had gotten a hold of some of it at some point. Where the "delivering dealer" is shown, all that is left is Michigan. But there is a line listed as "dealer code" and has the number 213 there. Is that number assigned to a specific dealer and would anyone know who it would be?
Thanks!