Department of State Diplomatic Security Service Challenge Coin, With 3D Case. This is a great looking United States Department Diplomatic Security Service challenge coin. Coin has reeded edges and is about 1 9/16" in diameter. All details are raised lettering and gold plated. Coin is contained in an acrylic airtight holder. The United States Diplomatic Security Service (or DSS) is the federal law enforcement and security arm of the United States Department of State. The DSS is the lead U.S. law enforcement organization abroad, and is the most widely represented law enforcement agency in the world. Its duties include protecting U.S. diplomatic missions, U.S. diplomats, and visiting foreign dignitaries; conducting criminal, counter-terrorism, and counterintelligence investigations abroad; advising U.S. ambassadors on security matters; and managing or implementing security programs worldwide.