They are certainly WW2 period, but could be post war. The date is often hard to read on these packets for some reason, as yours is. I have a similar packet dated 6.4 46 (or 48), another packet too worn to read the date and a third packet diagonally overstamped in red “TRACER” which is dated 2.6.50.
I suspect yours are British manufactured rather than Aussie, but I could be wrong. None of my packets have the side label with the “Watertight” marking though. I would appreciate a picture of this if possible.
The colour of the printing on the label indicated the safety class of the ammunition up until the late 1950s when black seems to have become standard.