Yes, it’s a “slammer”. In the POG game, these are heavier metal discs dropped onto your opponent’s stack of cardboard discs (originally the caps from passionfruit, orange and guava juice bottles branded ‘POG’ for the fruits’ initials) to knock them over. Caps falling face-down are restacked and the game continues until one player has none that land face-down.
POG drinks were first sold in 1971 and the caps used thereafter but the game wasn't commercialised under that name until the 1990s. Since the 1920s, cardboard milk bottle caps had also been used for similar games.
There’s one here, also marked ‘Team Kwik’ (presumably the manufacturer) but with a ‘ban-the-bomb’ symbol on the other side: