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 standard bullion sizes, including the large two ounces of silver format - such as this coin.
This coin is the "companion" to a twelve-coin set which issued as a sort of continuation of the Perth Mints Gods of Olympus series issued in 2014 (featuring Zeus, Poseidon and Hades), followed by the Goddesses of Olympus series issued in 2015 (Hera, Athena and Aphrodite); these were both issued under the authority of Tuvalu, but the continuation was issued for the Cook Islands.
The Mint says about it:
To complement the Gods of Olympus 2017 2oz Silver Antiqued 12 Coin Collection, this coin features the god of the underworld, Hades. In ancient Greek mythology, Hades was worshipped as the God of the Underworld and the ruler of the dead. In addition to the underworld, he ruled over all things beneath the earth. For this reason he was also known as the God of Wealth as he presided over all the precious metals still underground.
The coin has antique finish and a rimless design (which extends to the edge without a border). | 
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