These 5th Special Forces challenge coins are cast in heavy bronze with deep relief. Each coin is just over 1 9/inches in diameter and weighs in at just over an. One of the newest traditions in the world of elite military units is that of the Challenge Coin. If at the bar and you can show your 5th Special Forces challenge coin. Buy 5th Special Forces Group Silver Vintage Challenge Coin: Coin Collecting - forumtravelling.us ✓ FREE DELIVERY possible on eligible purchases.