Coronet flower pots.
‘Flower pot” buttons were mentioned in 1937-9 and 1946 newspaper articles so maybe these date from the 1930-40s. Carol shared a hand-painted version; see http://www.ausbuttonhistory.com/?p=14103
A mystery solved?
From 19th April 1950:
Could these cards below be examples? They certainly appear to be of a glazed ceramic material rather than plastic, with the colour underneath differing to that on top. I scratched at the coloured surface on one button; the colour came off to reveal a hard white material underneath.
The larger crimson buttons looks like the buttons on the far left of the photo. Although General Plastics Ltd did not have a factory in Victoria, they did have, at least from 1948 -1956, a warehouse in Flinders Street, and then Flinders Lane. They may well have sourced buttons from other manufacturers. It would still be interesting to find out who the Melbourne firm was.
Carol shares her collection of glazed pottery buttons, some which have similar shanks, but not necessarily the same. They are not Marie Gardner buttons, as those were not glazed over the complete back of the buttons. I am not sure they are by the same maker as mine. Perhaps there were several ceramic buttons makers in Australia?
In Britain during the war ceramicist Luxie Rie, became famous for her work for the Bimini glass studio and also for her ceramic pots and buttons. her buttons were more refined, and were made a decade before the above buttons.