Here’s how it works. Archaeologists found two Roman coins by a Roman-era building. On the right is a silver coin, known as an antoninianus, of Roman emperor Valerian II dated to A.D. 255.

Valerian was captured during the Battle of Edessa in 260 AD, making him the only Roman emperor to be taken captive. Not only that, but some sources claim that he was humiliated in captivity by the ...