My second favorite coin (to the Ben Franklin Half) has been the Panama Canal Octagonal $50 Gold Piece commemorative ever since I saw it on an episode of "Pawn Stars". It's design, low mintage, history, and shape are all reasons I love this coin. But I didn't really know much about it. Here's what I learned.
In 1917, the Panama Canal was finished. It is near the border of North and South America, and was built to ensure that ships wouldn't have to go all the way around South America to reach the other side of North America's coast. But this project was HUGE. And when you have a HUGE project, you need funding. And when the US needs funding, they make a commemorative coin. Hence, the Panama Canal commemorative series.
There are a total of five different coins made for this occasion, but I am highlighting the Panama Canal Octagonal $50 Gold Piece. The design was also made in a round version, but I like the octagonal one more. Only 645 of the octagonal pieces exist, and are very difficult to come by. Usually the Panama Canal Octagonal $50 Gold Piece appears graded as MS-63, though the highest graded is currently MS-66. It is the only US coin that is not round, and was designed by Robert I. Aitken.