1915 S Panama Pacific $50 Octagonal Gold Commemorative, NGC MS 65
$190000
According to Ron Guth:
In 1915, San Francisco hosted the Panama-Pacific Exposition, a massive celebration of the opening of the Panama Canal. To record the event, the U.S. Mint produced a variety of commemorative coins, including a Half Dollar, a Gold Dollar, a Quarter Eagle, and two versions of a $50 gold piece (one round and one octagonal). Attendees at the Exposition could purchase the coins singly or in a variety of combinations. The most extreme combination was a double set (two of each coin) housed in a specially made copper and glass frame. Because of the high face value of the $50 coins, sales failed to meet expectations, resulting in hundreds of unsold coins. These were eventually melted down, resulting in a net mintage figure of only 645 pieces.
The $50 Panama-Pacific gold coins are massive, heavy coins made of a relatively soft metal. As a result, the coins are susceptible to wear and damage, making it difficult to find exceptional examples. The vast majority of survivors are Mint State, usually in MS63. Gems are very rare, and the best examples top out at MS66.