The Cook Islands, a sovereign state in free association with New Zealand, uses two official legal tender currencies. The New Zealand Dollar circulates in parallel with the local Cook Islands Dollar; at the same time, the government also authorises many legal tender coins in the Cook Islands Dollar currency for collector's purposes.
Collector coins are dedicated to historical or general popular culture themes not related to the country itself. Many of them are in sizes based on the troy ounce, including the very large five ounces of gold format - such as this coin.
The Firefighter design is the second in the Real Heroes coin series by CIT Coin Invest.
The mint says about it:
This is the second release in our “Real Heroes” series that follows the immensely popular “Pilot” coins. This time, we focus on the Firefighter. Nobody will forget the heroism of the Firefighter facing unimaginable circumstances during the 9/11 attacks. Images of courage and bravery seared into our consciousness forever. More recently, we have seen many images of these heroes in action fighting the wildfires of the world.
CIT is proud to honor this “Real Hero” by presenting the most stunning coin ever done of the Firefighter. A tribute to not only those who gave the ultimate sacrifice during 9/11, but to all Firefighters that we count on to keep us safe. | 
Search for Cook Islands: Gold Five Ounces 2021 Real Heroes - Firefighter on eBay 