The Pokémon Company recently kicked off yet another distribution event for Pokémon Sword and Shield. Players can visit a participating retailer to receive a special code to unlock a Dynamax Crystal that can be used in the game to activate a Max Raid Battle featuring Gigantamax Copperajah at the Watchtower Ruins. The code for this event will be made available via the Pokémon Pass app at GameStop from August 14 to August 31 in the U.S.
August 14, 2020, update: This particular event has reportedly been canceled by The Pokémon Company International, but some GameStop locations are apparently still hosting it.
Source: The Pokémon Company