After your comment and an email, I tend to think I was in error. A closer look and the fact that the rings are not sprayed, after assembly, means it's probably just heat discoloration of some sort.

Either way, it's not a rare error, it's a flawed token.

I never took one apart to see what the colors look like, and since they are aligned, it's probably pressed on after both parts have been made.

There is a very thin line of silver color just inside of the brass ring. The goldish color has a rainbow effect. The reverse is the usual silver color, nothing unusual there.