Original CDV of John E. Shannon (1829-1866), a veteran of the Civil War, Co. E, 14th NY Volunteers. On the back is a period note saying that he died in 1866 and was buried in Dundee (in Hillside Cemetery there). According to Ancestrycom, Shannon died after being kicked by a horse!
My scan shows the front and back of the same CDV. It's 4" x 2.5" and in very good antique condition.