This is a copper or copper-toned keychain. It's metal, with a raised Sonic design & wiggly die-cut edge. The "Segasonic the Hedgehog" early era logo is stamped across him in further-raised letters at an angle. It is on a round beaded chain.
There is a whole set of these (notice that the shoe horn keychain is also this copper color metal) but the only known photo of the set is terribly small/poor & ancient. This is likely to be an uncommon keychain.