Who created Australia's Coat of Arms after the unification of the states and why? What do the symbols represent?

The Australian flag and the Commonwealth Coat of Arms at Australian Parliament House
Parliamentary Education Office (peo.gov.au)
The Australian flag and the Commonwealth Coat of Arms at Australian Parliament House

Parliamentary Education Office (peo.gov.au)
Description
At Australian Parliament House, the Commonwealth Coat of Arms (a kangaroo and an emu standing on either side of a shield) and the Australian national flag are clearly visible at the front of the building.
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Thank you for the question. Australia’s current Coat of Arms was adopted in 1912. 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.
There are many symbols included in the Coat of Arms.
There is a Coat of Arms on the front of Parliament House, which was designed by an artist named Robin Blau.