The 1915-S Panama-Pacific Octagonal $50 is the other half of a pair of $50 gold commemoratives the United States Mint struck to honor the 1915 Panama-Pacific Exposition in San Francisco. The Pan-Pac Octagonal $50 was struck in slightly higher numbers than its similarly large but round counterpart, with 645 examples of the octagonal struck versus just 483 of the round variety. However, both are regarded as highly rare coins and together represent two of the most famous commemorative coins the United States has ever made. They were made in conjunction with three other Pan-Pac commemoratives, including a silver half dollar, gold dollar, and gold quarter eagle.

The Pan-Pac Octagonal $50 was designed by Robert Aitken and shows a helmeted head of Minerva on the obverse and an owl, representing wisdom, on the reverse. Eight little dolphins fill the spaces between the outer edge of the circular obverse and reverse devices and the eight-pointed edges of the coin. The majority of Pan-Pac Octagonal $50 coins distributed still exist, and most of these are known in uncirculated condition. When they hit the marketplace, they are typically encountered in grades of MS60-64, with a couple dozen or so known in MS65 or higher grades. All Gems are reliably six-figure coins, while those in the lower grades generally realize prices in the strong five figures.