Royal Navy Reserve
According to Cossum, Stokes & Sons made uniforms for the British Royal Naval Reserve when they visited Australia. He dated them to pre 1910, but cannot confirm that. This design was used 1901-1921.
Melbourne Steamship Company Ltd.
In 1884 the Melbourne Coal, Shipping and Engineering Co Ltd became the Melbourne Shipping Co.Lts then in 1895 the Melbourne Steamship Co Ltd. They opened branches in Fremantle, Sydney, Adelaide and Newcastle. In 1961 the firm was taken over by Howard Smith Ltd.
NB: There was an earlier similarly named Melbourne Steam Ship Company 1864-1883.
New South Wales Military Forces
According to the AWM, this button was sewn onto a volunteers 1887 era tunic, but was removed and replaced with an appropriate silver button, as only permanent and partially paid (Militia) members wore gold coloured buttons and lace. Volunteers wore silver (white metal).
Below is a similar white metal button.