On page 71 of “Buttons of the Defence Forces in Australia” by J. K. Cossum, printed in 1988, is an image of a button bearing the letters VWAAC. Cossum notes that it was “thought to be Victorian Women’s Army Ambulance Corps.” Cossum did not have the luxury of the internet with resources like Trove ( https://trove.nla.gov.au/newspaper/?q=#) to research. Rather, it was the “Volunteer Women’s Army Auxillary Corps” from WW1.
The corps was formed under the control of the Commonwealth Defence Department. They aimed to welcome home returned soldiers and help with repatriation. They helped sell YMCA fundraising buttons, prepared “welcome home” suppers and met returning soldiers at railway stations. Apparently there was some disparaging comments about the corps, which they found insulting. The British version, of which Queen Mary had been the commander-in-chief, had approximately 10 thousand serving in France in 1918, working as cooks, clerks, waitresses, bakers, driver mechanics, assisting the Royal Flying Corps, sail making, as fitters and turner, etc.