Carnelian intaglio ca first century A.D. in later mount.
The mildly domed intaglio is depicting three mounted riders. Interestingly the riders are not armed. Could be depicting a historical event..?The shape of the gem ,being “cushion” shaped is also quite unusual.
The modern mount is 18 ct yellow gold.
Size of bezel: 23 x 17 mm
Ring size: “R” + 1/2 = US 9