Some people still consider the alterna to be a seperate species, but they are widely accepted as a distict subspecies of Lampropeltis mexicana (L. mexicana alterna). As far as locality, if it wasn't sold to you as a specific locality, it is likely of mixed origin. It may have been a retired or unwanted male from a breeder that breeds locality greybands (or possibly even a WC, but I sure hope not...), but it is tough to tell just by looking. Either way he is a looker, nice pick up.

-Evan