The Mudgee Guardian, on 26th September 1871, recorded the following: "Through the courtesy of Mr. Stewart, the Manager of the Joint Stock Bank, at Gulgong, we were yesterday shown a nugget weighing 38 oz 3 dwts 20 grs [12 kg]. This is the largest nugget found at Gulgong. It was found in a block claim between No. 1 and the Prospectors' on Happy Valley at a depth of 130 feet; it is of pure gold without any admixture of quartz" (source: State Library of NSW).
It was common for miners to store their gold at banks, and the gold rush gave rise to the prominence of new banks in Australia.
The Australian Joint Stock Bank was a bank in Australia. It operated from 1852 (by an Act of the New South Wales Parliament) to 1910, after which it became the Australian Bank of Commerce and then was taken over by the Bank of New South Wales in 1931. In 1931, the Bank of New South Wales (now Westpac) acquired the Australian Bank of Commerce.