A humble five-cent coin with a storied past is headed to auction a century after it was mysteriously minted, and bidding is expected to top $2 million. The 1913 Liberty Head nickel is one of only five known to exist, but it’s the coin’s back story that adds to its cachet: It was surreptitiously and illegally cast, discovered in a car wreck that killed its owner, declared a fake, forgotten in a closet for decades, and then found to be the real deal. It all adds up to an expected sale of $2.5 million or more when it goes on the auction block April 25 in suburban Chicago.