I don't know the context of this piece, but I believe that it is a piece of personal jewelry. It appears to be made of silver. It is printed (if that is the correct description for the process) with "A.E.F" (American Expeditionary Force), and is engraved in script with "A K Frost" - "5th Regt." - "U.S.M.C.".
I remember that there was a tiny 2nd Division Indianhead emblem where the empty post-hole is now. It was loose then (perhaps 50 years ago), and has obviously been lost since then.