This is one of five caches that need to be found to unlock the "key" to the above-referenced cache. Each of the five is named after a World Series of Poker Main Event champion.
You are looking for a small piece of an EJMG, which is a plastic thing that folks use to get lids off jars. [Think 2-D rubber.] Be careful while retrieving/replacing!
FTF HONORS GO TO jratzlaf!!!