Well, bulbapedia says the release date was June 2004. Hidden Legends came out that same month. FRLG released in September so too late for kit's release date. It has to be Ruby/Sapphire, Sandstorm, Deoxys, TATM, or Hidden Legends. The rulebook in the box, which has designs and example cards specifically in this kit, talks about TATM and Hidden Legends theme decks and boosters, so would it be more likely to be one of those?