Hi Alex, What you have there mate is an English made rising sun badge from ww1. They are commonly and incorrectly refered to as a lighthorse badge by inexperienced collectors, but they were actually made as replacement badges for the Australian soldiers serving in France. They were made both with and without the slider, the others having the standard lugs on the back. Now having looked at yours It seems it was made with a slider to begin with and it has been removed at some stage and had a hole drilled in the centre of it, perhaps to be mounted to a display board with a screw or nail and then later on in It's life It had the slider replaced. Also interesting is the manufacturing error where the piece on the left next to the scroll hasn't been punched out.
I hope this helps mate.
Hi Luke, Thanks for the history. I don't collect this stuff but just got it because it looked interesting. All the best, from a cold,damp UK. Alex