Courtesy of the British Museum

Two in one. This double ring from the first or second century C.E. consists of two flattish hoops soldered together, with a circular convex garnet in each setting. The hoops intertwine at the bottom of the ring to form a Hercules knot, a common symbol of the hero’s protective powers. These garnets typify uninscribed gems in rings, because they are rounded (called cabochons) rather than faceted. Single rings with such rounded stones were very common in antiquity.