NGC 1971-1976-S proof Ike dollar 40% silver planchet. The planchet was intended for striking into a proof 40% silver Ike dollar from the 1971-1976 era. As a planchet, it has a raised rim, and also the coin's surfaces are glimmering, and have the fine burnishing marks from the medium used to burnish proof planchets to a mirrored surface.
There are a relatively small number of these known. Our estimate would be around 50 of the proof 40% silver Ike planchets are known.