Very good question, I asked that myself when I saw them ,This is what it says on the back of the deck.( Washington DC-1943) This special deck of spotter playing cards has been prepared to assist you in learning the characteristics of FRIENDLY and ENEMY aircraft. While the primary purpose of these cards is to show is to show you how one type of airplane can be distinguished from another, we have, by adding regular playing card indexes, created a combination; entertaining and educational. .