This is either Walther "Juno", or the Crown Crystal version known as Six Swirls, unless there were other factories making the same pattern. You find them with slightly different curvature of the question mark panels, and I think yours is Australian, but I couldn't be absolutely certain. Where are you based?
The Australian pattern was first seen after mid-1930s (exact date unknown as the catalogues are missing). The frosting is characteristic of the Australian pieces, but is also found on others so it's not definitive.
Edited to add: Stephen, thank you. Six Swirls it is!