It appears from the research of others, that this medal, or one like it, was pinned to the hats of soldiers in France. Which solders (French or American) we don't know.  Research also  says that a veterans group in the USA, The American Legion, created the organization called "40 Horses and 8 Men" (40 Hommes 8 Chevaux) in 1920. As in the depiction on this medal, French boxcars took US soldiers to the front lines during WWI. Those boxcars were known to carry 40 men or 8 horses.  The transport of the soldiers is depicted in the scene on the medal where an America soldier with bayonetted rifle watches the train as another soldier looks out of the boxcar, his horse standing behind him. (see Pritzker Military collection/museum.)