The symbols were created by vexillologist Whitney Smith and then adopted by the International Federation of Vexillological Associations (FIAV) in the early 1970s.
[1] Vexillologist Željko Heimer added the symbols for normal and historical in the early 1990s.
[2] Vexillological symbols describe information on a flag's recognition status and design.
The usage symbols are based on a grid of two rows representing use on land and use on water, and three columns representing private use, public use, and military use.
Heimer suggested an additional row for air ensigns, but it has not been adopted by FIAV.