Nubia was introduced to DC Comics readers in the winter of 1972-3 in the pages of Wonder Woman, as Diana returns to Paradise Island (now Themiscyria), and is shocked to discover she has a "twin sister", who has the appearance of an African-American. I Ching, Diana's mentor when she was powerless, is killed off in the same issue to create the transition.
In 1976, Mego added Nubia to their line of action figures, as part of a sub-line with Diana and her on-again-off-again beau, Steve Trevor. Check this ad: