More than 100 dodecahedrons have now been found in northwestern Europe, but archaeologists still don't know what they were used for.Amateur archaeologists in England have unearthed a stunning Roman dodecahedron — a mysterious class of objects that has baffled experts for centuries.The dodecahedron — a 12-sided metal shell about the size of a grapefruit — was found this past summer during a dig in a farmer's field near the Lincolnshire village of Norton Disney, located about 35 miles (56 kilometers) southeast of Sheffield.A previous geophysical survey, which had detected underground areas where the Earth's magnetic field had been disturbed, had...