Niue, a sovereign state in free association with New Zealand, uses two official legal tender currencies. The New Zealand Dollar is the circulation currency for daily transactions, while the government also authorises legal tender coins in the Niue Dollar currency for collector's purposes.
A number of mints issue a large variety of commemorative, bullion and collector coins under the authority of Niue. These coins are dedicated to historical or general popular culture themes not related to Niue itself. Many of them are made using "smartminting" techniques and have features not generally found in circulation coins - e.g. high relief, full colour printing and/or different forms, including fully three dimensional (3D).
Some coins are marketed in standard bullion sizes, like half ounce silver, one ounce silver etc, and some of those are also denominated as $1, for which see respective lists; this particular coin denominated as One Niue Dollar is not in a standard ounce-based size.
This coin is part of a Mint of Poland series featuring the Chinese Lunar Calendar and is dedicated to the 2021 Year of the Ox (12th February 2021 - 31st January 2022).
The Mint says about it:
"According to the Chinese Zodiac, the ox is a symbol of confidence, patience, stability, and financial growth, while the number seven, which is also depicted below the ox, stands for perfection, happiness, and harmony.
The coin is created from the finest silver. It has an extraordinary design inspired by Chinese astrology and is rich in original and stylish decorations, such as laser frosting and digital printing." | 
Search for Niue: One Dollar Silver 2021 Year of the Ox - Seven Elements on eBay 