That medal is listed in the Eglit book on medals of Christopher Columbus as E-55. It also comes in white metal, gilt, and aluminum. In perfect condition, it can bring $200-$300. In condition such as yours, it may have a value of $20-$30 on a good day. It is a very common medal in that condition. It's a medal that either brings high dollar value ($200-$300) or low value ($20-$30) with little in between. Being that it is 50mm, it is not a so-called dollar. You can identify other Columbian Expo medals at my website http://www.1893columbianexpo.com
Man, I love those Columbus tokens /medallions you guys got....well done!! Id love to get my hand on one..what a wonderful keepsake.
Thanks. I've got a lot more medals from the WCE; I just haven't uploaded them yet. I realy need to redo the inventory and get pictures up there. One problem is the huge number of unlisted pieces.