1999 Base Set Black Triangle Error Booster Pack Set PSA 10 The very first expansion to be released for the Pokmon TCG was Base Set (Expansion Pack in Japan), and in front Booster Pack [Triangle Error] Prices Pokemon Base Set Pokemon Cards 1999 POKEMON BASE SET BLACK TRIANGLE ERROR VENUSAUR BOOSTER PACK PSA 10 If you happen upon an unopened #Pokemon pack and notice a little black triangle on the bottom right, then it's your lucky day. Those packs are known as "Black Triangle Errors" and 2 insanely rare Pokmon Base Set Booster boxes!!!, ., ., ., ., #pokmoncards #charizard #pikachu #pokemoncardcollection #pokemoncard #pokemon Opening 3 Original Pokemon Base Set Boosters