I've never heard of these being a tradable thing. I know we got coins for working Epcot's 30th but they were presented as CM only and not something we should ever sell for profit etc. after researching what a challenge coin is I think the ones they gave us are replicas of challenge coins they gave out to all Epcot CMs on opening day. I know security received a different set at some point as well but newer security may not have them.