The magazine "Game Players" had a promotion for Sonic during the time of Triple Trouble for the GameGear. They released a set of pogs (or milk caps) that came free with an issue of the magazine. As you can see here, the art for the fronts has been 'stamped out of" larger pictures probably including the game box for Triple Trouble. Still, they're not a bad freebie, as pogs are still good to collect.