The discovery of gold in the colony New South Wales in 1851 prompted a surge of immigration among prospector seeking wealth in the new colony. While the lands were resource rich, the colony lacked the facilities to monetise the gold and the process in sending the gold to London for monetisation was slow and expensive. To help resolve this, the Royal mint sought to open a branch in Sydney so that the gold would not need to be shipped to London to be coined. The Sydney mint opened in 1855 in the rear of the Rum Hospital, situated on Macquarie Street in the Sydney CBD(Sydney Mint Museum, 2017).
The first business strike half sovereigns struck at the Sydney Mint were dated 1855 and 1856. Rather than using copper to harden the metal as the Royal Mint did, the Sydney Mint used silver(Melbourne Museum Discovery Centre, 2008). The reverse design featured a banksia wreath tied into a bow, below and surrounding the word AUSTRALIA; these are positioned below a crown with the legend SYDNEY MINT and HALF SOVEREIGN encircling the entire design. This was the only time a colony would ever deviate from the imperial design though it was short-lived with the Sydney Mint reverting to the imperial shield design in 1871.
Excluding varietiesand overdates the key date of the series is undoubtably the 1855. Both the Type I and Type II 1855 dated half sovereigns are extremely rare with the former being survived by approximately 55 to 60 examples and the latter with just 3. The 1860 is also rare with about 200 to 250 surviving examples.
The Sydney mint series is marked by low survival rates, likely due to the gold-silver alloy giving them a higher intrinsic value than their face value making it profitable to melt them down for their metal content. This gold-silver alloy continued for the entire series despite official protests to the Colonial Treasurer by Sydney based chemist Charles Watt with the Mint Master arguing that the extra value from the silver content was a decided advantage(Watt, C., Ward E. W. and Lane, H., 1863).
The Royal Mint produced 4 patterns dated 1853 which feature a slightly different reverse design, only one pair of sovereign and half sovereign exist in private hands.