First World War handkerchief, 1916. BT 52/3130
Many handkerchiefs were produced during the First World War with designs that commemorated or recorded aspects of war. They were commercially produced for soldiers to carry with them, or to give to those back home as mementos. It is likely that the authors of these letters would have done so.
Manufacturers and designers would send illustrations or examples of their work to the Board of Trade in order to obtain copyright protection, and The National Archives now holds these records. This design serves as a record of some of the allegiances of the time.