U S NAVAL CRIMINAL INVESTIGATIVE SERVICE Challenge Coin. This is a great looking United States Naval Criminal Investigative Service commemorative challenge coin. Coin is about 1 9/16" in diameter. This coin has a badge design of the United States Naval Criminal Investigative Service on one side and raised U S Navy emblem on the other side. The United States Naval Criminal Investigative Service (NCIS) is the primary Law enforcement agency of the United States Department of the Navy. Its primary function is to investigate criminal activities involving the United States Navy and U S Marine Corps, though its broad mandate includes national security, counter-intelligence, counter terrorism, cyber warfare, and the protection of U.S. naval assets worldwide. NCIS is the successor organization to the former Naval Investigative Service (NIS), which was established by the Office of Naval Intelligence after the Second World War.