That looks to be so-called dollar size and the name is appropriate. It is a miniature size of the actual award that was given to Emmerich at the Columbian Expo. About 22,000 awards were given at the expo and companies used there awards in their advertisements. Emmerich had these minis made for their advertisement. It comes in 2 versions, Chas. Emmerich and Emmerich. I have also seen the Kimball company (pianos) have the same medals. I actually have this medal in bronze as issued as well as a trial piece in aluminum.
In this condition, I'd bet this would sell at most for $50. If you get a couple of crazy bidders that haven't done their homework, you might see more for it. I can understand why Heritage would say $100 or less. Worn and corroded versions are generally available and therefore, don't carry much value. It's the really nice, unworn pieces that can bring a couple hundred bucks.