This simple key chain is a rounded long shape of silver-tone metal with an engraved design of finger waving Sonic in the middle. The top simply says "Sega" in the classic font. Was this one of a set with other characters? Sets like those were common for the time, so it is likely. 

Its 'ring' has a screw-shut closure which is one of the more secure types. The keychain itself is just a basically rounded-ends rectangle shaped flat piece of metal with finger-waving Sonic & the Sega logo on it. It looks like it was stamped into the metal or left off when the metal was given the 'satin finish' you see here. It looks like it's taken a bit of wear in this photo.
The right-side photo shows the item when it is new in the bag. With this, you can really see the shiny texture for Sonic/Sega logo, & how the rest is satin finish.