It's no surprise that proof set values are linked to the metal of the coins, but this super-valuable gold proof set is...well ...

a 1920 Indian Head Gold Coin in circulated condition is worth between $20,000 and $75,000. But that value rises to as much as $2 million for specimens in pristine, uncirculated condition.

Circulating coins are worth $408,000 to $409,000 in average condition and upwards of $1.1 million for uncirculated condition. In 2009, the Strawberry Leaf penny broke records for the most money ...