The Two Cent AEF Pane
Wars require the movement of troops and material, and this requires communication, which means mail. The hundreds of thousands of Americans who were sent to fight and die in France at the end of World War I were sent with two postal issues all of their own. Soldiers like booklet stamps as they can be carried in backpacks. The cardboard covers keep the stamps somewhat safe from damage, and such booklets are easier to store for when they are needed. And WW I was the war of the trenches. Between the senseless running toward machine guns for a few feet of gain which were called battles in that war were long periods of inactivity in the trenches. There is just so much time you can devote to playing cards, and these men had lots of time to write home. Ordinary booklets were used up too quickly, so the Post Office created booklets of thirty stamps of the one cent and the two cent values just for the soldiers of the American Expeditionary Force in France.