We in the UK used to use SWG, also wires would be given by strands/diameter (e.g. 3/0.029 for 3 strands of 0.029" diameter each, about 1.3mm2 CAS typically for light circuits, etc).
These days it is all the CSA that is specified, which helps a lot for sizing circuits!
These days it is all the CSA that is specified, which helps a lot for sizing circuits!