A nearly 1,800-year-old silver military medal featuring the snake-covered head of Medusa has been unearthed in what was once the northern edge of the Roman Empire.Excavators discovered the winged gorgon on June 6 at the English archaeological site of Vindolanda, a Roman auxiliary fort that was built in the late first century, a few decades before Hadrian's Wall was constructed in A.D. 122 to defend the empire against the Picts and the Scots.The "special find" is a "silver phalera (military decoration) depicting the head of Medusa," according to a Facebook post from The Vindolanda Trust, the organization leading the excavations....