9 most valuable U.S. coins
6. Liberty head nickel
90% silver, 10% copper
This nickel is extremely rare, with five known examples. All five were sold in 1924 by numismatist Samuel Brown, a former U.S. Mint employee. Brown's sudden ownership of the heretofore unknown coins has led to fair amounts of speculation. Some think Brown struck the coins himself. Others believe he stole them.
The coin was featured in an episode of the original 'Hawaii Five-O' (The $100,000 Nickel). Of the five known examples, three are in museums. If one of the Liberty head nickels were to be uncovered — and it was in perfect condition — it likely would fetch upwards of $20M.