I think this is idea who's time has come. I just received a 2004 WA geocoin as a gift from my sister and showed it around at the Tucson event today to appreciative comments.   These coins are outstanding and the photos do not do them justice.  They have a clear lucite? material over the enameling to protect them  and also it gives them a slight convex surface.  Don't know who made these, but they are great.   Also I know a cacher here in Tucson who is a graphic artist, has designed enamel pins before, owns a jeep and might be willing to help with designing.
Golefts
P. E. Thompsen