WWI era sterling silver pendant locket featuring an Australian soldier

World War One era, sterling silver, pendant photo locket containing two greyscale portraits of Australian soldiers.
The first soldier is wearing a high collared greatcoat over his uniform, and a peaked cap with a Rising Sun cap badge affixed to the centre of the band. He is not looking directly at the camera, but on an angle. His eyes are very striking, being a lighter colour surrounded by very white sclera.
The second soldier is wearing his uniform and peaked cap. It is possible it is the same soldier or perhaps a brother, as they have very similar features.
The locket has a hinge on one side and opens out to reveal the photos. These are held in place by the silver edging and protected by a celluloid cover, some of which has deteriorated over time.
There is a loop attached to the top of the left hand side of the locket, through which a chain is threaded. The silver mark 'STG' is impressed at the bottom of the outside of the right side of the locket.
Dimensions shown are for the closed locket and don't include the chain.