Thunderbox is a Japanese fashion clothing brand.
It seems in 2019 at some point, they did a collab with classic Sonic. This produced several shirts, shorts and a few hats. (All of which can be seen on Gear Accessories and Gear Clothing) however, they also did 2 little metal and enamel pins. Here, you can see them mint on their card/factory photo. The game boxes show you about how big they are.
You could get running stock Sonic where he's in profile, or the neoclassic art of fleeing Eggman where he is running with arms out dramatically. Notice that the Eggman pin is a good bit larger than the Sonic one, maybe they were going for a bit of scale? Either way, it's a good move. Both pins are quality and look nice, every detail is present & the colors are nice and bright. These are a good addition to their Sonic collab line.