Authentic Cook Islands 2011 “Famous Naval Battles” silver proof coin commemorating the Battle of Midway (1942), one of the most decisive naval battles of World War II. This issue contains 1 troy ounce of. 999 fine silver and features a high-quality proof finish. The coin is housed in its original government packaging (OGP) and includes the original Certificate of Authenticity (COA). Individually numbered example #1038, as shown. Issuing Authority: Cook Islands. Series: Famous Naval Battles. Theme: Battle of Midway – 1942. Weight: 1 Troy Ounce. Packaging: Original Government Packaging (OGP). Legal Tender: Cook Islands.