Qantas has changed its logo and uniforms multiple time since its inception in 1920.
In 1934 Qantas and Imperial Airways (a forerunner of British Airways) formed Qantas Empire Airways Limited (QEA). The first services were between Brisbane and Darwin, extending to Singapore in 1935. Most of the fleet were used for war service during WW2. Post war, services were extended to Britain.
In 1944 a kangaroo logo was first introduced. In 1947 this changed to a blue ‘flying kangaroo’. In 1968 the flying kangaroo turned red. This logo lasted until 1984 when the wings were dropped.
These buttons have no backmarks, and may have been made in China, as the uniforms were.
In 1934 there was a smart new uniform of khaki. The tropical uniform consisted of “biscuit coloured shorts, shirt, and tunic, with a khaki sun helmet.”
The crew uniforms were changed in the years , 1959, 1965, 1969, 1971, 1985, 1994, 2003, 2008 and 2016.
Thanks to Darren for information on dating the buttons.