Marine Corps Security Force Regiment Challenge Coin. This is a Marine Corps Security Force Regiment challenge coin. Coin is about 1 9/16" in diameter and beautifully detailed on both sides with raised lettering and reeded edge. Coin is contained in an acrylic air tight holder. The Marine Corps Security Force Regiment is a dedicated security and counter-terrorism unit of the United States Marine Corps. It provides security forces to guard high-value naval installations, most notably those containing nuclear vessels and weapons. It also provides Fleet Anti-terrorism Security Teams (FAST) and Recapture Tactics Teams (RTT). Marines who complete Security Forces training are assigned a secondary Military Occupational Specialty (MOS) of 8152 (Marine Corps Security Force Guard), while instructors can earn 8153 (Marine Corps Security Force Cadre Trainer).