australian banknotes history, page-3

The discovery of gold in 1851 led to the minting of Australia's own gold coins and spurred the development of banking. Commercial banks issued their own notes backed by gold, though people were often wary of them particularly after many banks failed in 1893.

Without further reading it reads like the private banks did not have the amount of gold necessary to back their privatley issued notes a simmilar situation to what may be occurring in tether