18 December 1915 usage from the Panama-Pacific International Exposition, Department of Coins and Medals
2¢ stamp with “PPIE Co” perforated initials (Panama Pacific International Exposition Company)

A set of commemorative stamps, 1¢ to 10¢, was issued for the Panama-Pacific Exposition that was held in San Francisco in 1915. The sponsoring Company perforated their initials on stamps as a control measure to prevent theft. The cover is addressed to a coin and medal dealer.

1915 Panama-Pacific Gold Dollar minted in San Francisco

A quantity of 15,000 commemorative Panama-Pacific gold dollars were minted in January, 1915 as part of a set of commemorative coins ranging from 50¢ to $50. The obverse design represents a laborer on the Panama Canal and the reverse shows two dolphins representing the joining of the oceans.