This happens way too often with Steam Booster Packs : r/gaming
Pokémon TCG: XY: Steam Siege - Prerelease Kit
Steam Community Items (Documentação do Steamworks)
Steam - opening 11 card booster packs - YouTube
How many Booster Packs did You get? In 5 years I only got 3 of these : r/ Steam
Amazon.com: Pokemon TCG: Steam Siege, Blistered Booster Pack for 72 months to 1080 months, Containing 10 Cards Per Pack With Over 110 New Cards To Collect : Toys & Games