An eight pointed star overlain by a wreath. In the centre the rod of Asclepius inside a circlet inscribed ‘Australian Army Medical Corps’. Above is an Imperial crown displacing the top point of the star. Over the bottom point of the star a scroll inscribed ‘Paulatim’.
This example in blackened brass. To the reverse two loops E-W.

Festberg illustrates three similar versions of the Imperial crown badge, another has the wreath close up to the edge of the circlet and was worn during the same period. The third similar but with the ‘Royal’ prefix to the title and worn 1949-55. The Queen’s or St. Edward crown type was introduced in 1955.

References:
Festberg, Alfred N. Australian Army Insignia 1903-1966 (Amazon UK link)