DDJ is the same pickup as a modern SH-6, not a custom or variant. "DDJ" just means a Duncan Distortion that was wound by Maricella Juarez (aka: "MJ") before she moved to the Custom Shop. Typically, these were made throughout the '80s to early '90s and are named as such because the label on the bottom would say "DDJ". But in terms of construction and design, they aren't any different than the production SH-6 you can buy new.