These are "Acrylic Key Charms"
They're not really key-chains as they are probably rather small. They're clear acrylic plastic, with the color for the sprite design embedded in there/or sometimes sandwiched between acrylic layers. Each has a pixel 16 bit look & is classic. You can get running Sonic, blur shoe Sonic, running Tails, flying Tails, running Knuckles, gliding Knuckles or running Eggman. But why is Eggman the only one faced left? Notice they have little 'lobster claw' style small clasps rather than rings. That bit under each one is probably a lead-loop so they could be hooked together, or to other litems, like a charm. These ARE a "Sega 60th Anniversary" product.