PCGS 1970-S proof Kennedy half dollar struck on an Aluminum Missouri Shell gas token. The aluminum token was issued by Shell gas company as part of a promotion for its gas. People could collect the aluminum tokens and get prizes for them. Somehow, this token ended up inside the Mint and was struck in a press striking proof 1970-S Kennedy halves, resulting in this coin.
A rare and desirable major Kennedy half off-metal, and one of the few aluminum off-metal Kennedy halves known! Aluminum is not a metal type that often comes on U.S. off-metals since we did not use it to strike regular issue U.S. coins.
The coin may have been intentionally made, or it is possible that, being a "factory" as it is, a scenario such as an employee accidentally threw a few of them into a planchet bin when he saw a few of these lying on the factory floor, and since they are nearly the same size and color as a silver Kennedy half dollar, and they were then struck and got out of the Mint through normal channels. We likely will never know, but it is an incredible off-metal, and quite rare, with only about 3 or 4 Kennedy halves known struck on aluminum tokens similar to this.
This particular coin is struck on a "Missouri" state Shell coin game token (we show a photo of the token this coin is struck on, below, and it will be included with this coin to the buyer.)