Series Name
The image below is taken from the top margin of a trench map.
Common series names were "France", "Belgium", "France and Belgium", "France and part of Belgium" and " Northwest Europe". Several series of special purpose maps were also common during the later part of the war such as "Situation" maps, "Positions" maps, "Enemy Organisation" maps and others. That being said, many trench maps were printed devoid of any series name or sheet title.