ANACS 10c 1998-P Roosevelt dime struck on a Lincoln cent planchet. The cent planchet was "cut down" to fit into a dime press, with the zinc exposed on the coin's edge. The planchet was likely cut down to size by a Mint employee, who then struck them in the dime press. The coin is copper on the obverse and reverse, and has the zinc inner core.
These are quite rare, with just 6 or 7 known for the entire Roosevelt dime series combined! Of the known examples 5 or 6 are cut down cent planchets, and only 1 we can confirm is on a full weight cent planchet. A rare off-metal, and missing from most off-metal collections.