Minecraft wiki entry for Explorer_Map, associated text: It should be noted that this additional data is stored in the Cartographer's NBT data and in the inventory item's NBT data, and not in the map file (e.g. map_0.dat). If the player were to use the /give command to give themselves a map with the same map ID as an existing explorer map, it would still have the Ocean Monument or the Woodland Mansion icon on the map, but it would simply be named "Map" instead of, for example, "Ocean Explorer Map".