The silver coin is a Fast Pass token, which you have earned for playing over 1,000 total songs!

Each token will cover the credit(s) charged for the Fast Pass play of one song. The token is applied to your account daily (24 hours after the previous token(s) was added).

You can earn up to 2 Fast Pass tokens every 24 hours. Play 3,000 songs to unlock the second token on your account, which will refresh every 24 hours.