I don't know what it is, but the black coating on my Al Mar Sere 2K looks nice and it is very tough. It has smoothed and "thinned out" a little to where the bevels show through a little bit but it has been really scratch resistant.
I really like a mirror finished blade, but once it gets scratched - Uhg! I agree that a stonewashed blade is probably the most practical but I don't really like how it looks. It sort of looks like those cheapo sheets of galvanized tin.