"something gotten at the fair" That thought crossed my mind right away when I saw it. I remember being at the fair when I was a kid. In the arcade there was a machine where you could put a penny in and it would flatten it and stamp something onto it. The pennies came out flat and oval shaped just like your token. It looks like silver so maybe your GF used a quarter to do something similar ? Dunno, a quarter was a lot of money back then so maybe not ? It could also be a key chain fob companies gave away for buying something ?
It's pretty damn cool whatever it is.