This is for the absolute Grail of Star Wars, Empire Strikes Back, Return of the Jedi, or POTF Coins. Supposedly there are only 5 to 10 known examples of the very Early Luke Skywalker Prototype Coin. This coin represents the very early design phase of the Power of the Force concept, although it does not mention Power of the Force on it.
More information can be found at ToysRGus — I mean the Star Wars Collector Archive:
http://theswca.com/images-coins/proto-lukejedi.html
