Here's an actual classic keychain of Knuckles. He's likely PVC or some other mostly-hard plastic. This was made in 1994 (Stamped on the back of his head) It's fully 3D, & Knuckles is having a facial expression with one fist somewhat raised. (so, its not his default pose) The likeness is pretty good. Notice the original paper tag, it was made by Sony Entertainment FOR Sega, at that time. Also look at the ring, it's sort of "G" shaped, which is unusual, but probably the same for all keychains in the series. (likely at least Sonic was also made) This is in the SonicGear collection.