As with the 1915 Panama-Pacific International Exposition commemorative half dollar presented above, the official medal of the Exposition also featured a cornucopia as part of its design.
The medal was struck by the US Mint via a press installed within the Mint's exhibit on the Exposition grounds; bronze, silver and gold-plated bronze versions were produced. The medals were classified as So-Called Dollars (SCDs) by Harold Hibler and Charles Kappen and included in their landmark book/catalog published in 1963; they are assigned the HK #s 399-401.
On the obverse is seen the figure of Winged Mercury, the swift messenger of Greek mythology, symbolically opening the locks of the newly-completed Panama Canal to allow Argo the swift and magical sailing ship of Greek mythology to pass. The Argo carried Jason and the Argonauts on their voyage to obtain the fabled Golden Fleece. On the medal, the Argo was meant to represent the swift sea travel now possible via the Canal.
The reverse design features two female figures that are meant to symbolize the East and West Hemispheres. They are depicted sharing full cornucopias
with the earth behind them showing North and South America. Below the figures is seen a seagull, a common bird of the Canal Zone.
The medal was designed by Robert Aitken, the artist who also created the designs for the Panama-Pacific gold $50 coins.
Here's my gold-plated bronze medal (HK-401):