The Panama-Pacific Exposition of 1915 was a huge affair, drawing crowds from all over the country and the world to view the various exhibits and displays and to celebrate the opening of the Panama-Canal. Five different coins, sold to customers at a premium over their face value, commemorated the event: a half dollar, gold dollar, $2.50, an octagonal $50 and a round $50. Demand for the coins varied depending on the face value; as might be expected, the $50 coins were weakest in terms of the number of coins sold and the half dollars were the most popular. In between were the $2.50 gold coins, the first commemoratives in that denomination. Charles Barber designed the obverse of these coins using a mythological hippocampus to transport the allegorical female figure of Columbia across the water. Columbia carries a caduceus as a nod to the successful medical triumph over the yellow fever that afflicted many of the canal's builders. The reverse, designed by George Morgan, was a throwback to his defiant eagle motif used on some pattern coins from the 1870s.
Total sales of the 1915-S Pan-Pac $2.50s reached 6,749 pieces. Those not sold were destroyed. Though some examples were spent, the vast majoirty of the issue survives in Mint State. PCGS alone has certified 35% of the total mintage, and their Population Report gives a good picture of the grade distribution. The most common grade is MS64, followed by MS65, then MS66, then MS63; hundreds have been certified in each of those grades. Superb MS67 examples are very scarce, due in part to the low relief of the design and the softness of the golden alloy.