Hello from Sweden!

"Telling the difference between an Eastern and a Western Ribbon Snake is quite easy: Western Ribbon Snakes have two sometimes fused white spots on the top of their heads; Eastern Ribbon Snakes do not. Ribbon snakes can be differentiated from garter snakes by their overall shape: they’re very elongate; their side stripes are higher up on the body (on the third and fourth scale rows — most garters’ stripes are on the second and third rows); and there is no black between their labial (lip) scales."

Source: Questions About Ribbon Snakes in Captivity - Gartersnake.info