Thank you for the question. Australia’s current Coat of Arms was adopted in 1912. Whilst not much was documented about the design from this period, there is a story that the design of the emu and the kangaroo comes from a Croatian migrant who trademarked it as a logo for his vineyard. You can read more about that story here.
There are many symbols included in the Coat of Arms. These are explained on the Department of Prime Minister and Cabinet’s website, It’s an Honour.
There is a Coat of Arms on the front of Parliament House, which was designed by an artist named Robin Blau.