Excavators in Hungary have discovered a "very rare" gold Roman coin that features the face of a murdered Roman emperor.The third-century coin depicts Emperor Volusianus, who co-ruled the Roman Empire for about two years with his father, until the emperor was assassinated at age 22 by his own soldiers. Because of Volusianus' short reign, coins bearing his face are rare. What's more, the coin's denomination is rare, as is finding gold coins from the Roman period in Hungary, said Máté Varga, an archaeologist at the University of Szeged in Hungary and head of the excavation.Despite their luck in finding this...