For 15 years these cards were rumored to exist, and reddit user loserchris has confirmed they in fact do.
Confirming the set IDs and existence of Elemental HERO Avian, Elemental HERO Clayman, and Cyber Dragon, we now no longer know the set IDs for Winged Kuriboh LV10, Black Luster Soldier, or what the identity of card 010 is.
source: https://www.reddit.com/r/yugioh/comments/ki1ttk/parallel_rare_cards_from_mf03/
