2015 Cook Islands Narwhal Silver Coin 1 Oz PCGS SP70 Unicorn High Relief Low Pop. The 2015 Cook Islands Narwhal Silver Coin is a highly sought-after collectible featuring a unicorn-like Narwhal design, minted with a fineness of 0.999 silver. The high relief design adds to its visual appeal, making it a unique and valuable addition to any coin collection.