RICHMOND, Va. — A humble 5-cent coin with a storied past is headed to auction and bidding expected to top $2 million a century after it was mysteriously minted.

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....