During World War II, USPC provided spotter cards, which illustrated the characteristic shapes of tanks, ships and aircraft from the more powerful countries. Each suit is dedicated to planes from four of the primary countries: Spades – US, Diamonds – Germany, Clubs – Japan, Hearts – Great Britain. The airplane edition continues to be the more popular deck as there are a number of facsimile decks still being produced today from a number of companies. Unlike similar decks created for other military countries in Britain and elsewhere which were simple flashcards without playing card elements, these decks made by USPCC doubled as standard playing cards and were made available to both the military and the public. In fact, the USPCC even took out ads in magazines for them, including the 1943 ad from Collier’s (see related scanned image). In addition, the US government established a network of civilian airplane spotters whose duty it was to lookout for any possible repeat of the Pearl Harbor attack, with numbers in this Army Air Forces Ground Observer Corps reaching about 1,500,000 volunteers, With that many members of the public involved, it becomes obvious the appeal this deck had and still does have. This PCDB entry is for the original deck released in the 1940s by USPCC. Facsimile decks have their own related entries.

http://a.trionfi.eu/WWPCM/decks07/d05768/d05768.htm