DLC = Diamond-Like Coating which is the coating bonded to the stainless steel in the space black watch casing and link band.
If you were to get, say, the classic buckle band and put it on the space black case, it will look stupid because the metal part that slides into the case is not space black, and neither is the buckle, though the buckle is a bit less of an issue.
Actually, it's Diamond-Like Carbon