New Zealand uses the New Zealand Dollar as its circulation currency for daily transactions. The country also issues a number of commemorative and collector coins, including in the internationally popular half gram of gold mini-coin format (abbreviated as 0.5 g oz Au, where "Au" comes from the Latin word for gold, Aurum). Authorised by the Reserve Bank of New Zealand, the official issuer of these coins is NZ Post - which also issues the country's postal stamps. Manufacturing of the coins is commissioned to various foreign mints.
The coins are "Non-Circulating Legal Tender" (NCLT) and not bullion because they are issued at prices much higher than their intrinsic value and are targeted at collectors who appreciate them for their artistic or sentimental value, and not at bullion investors.
NZ Post says about this coin:
This delicate and minuscule 11mm 0.9999 gold proof coin weighs in at just half a gram. The design of the New Zealand 50c coin is minted in fine detail, with the Ian Rank-Broadley portrait of Queen Elizabeth II on the obverse.
The illustration on the reverse features the HMS Endeavour, the ship on which Captain James Cook became the first Briton to reach New Zealand, and Mount Taranaki in the background. Used in Captain Cook’s first of three voyages to New Zealand, the Endeavour would have passed by Mount Taranaki early in the year 1770 as it was sailed down to Ship Cove in the South Island after first anchoring in Turanganui (Poverty Bay) in the North Island. | 
Search for New Zealand: Gold Half Gram 2021 Endeavour on eBay 