Sixth-plate ambrotype in half of a case. Very good or better antique condition behind mat and cover glass. Written inside of the case is an ID of John Arthur Brampton, Age 11, 1854... so this could possibly have been John's sister, Agnes Jane Brampton, who was born in 1838 (d.1922), making her about 16-18 years old here. I think it's a good possibility this is Agnes because her brother was born on the Bayeux Estate in Old Greenwich, Connecticut, and one or two other images picked up along with this ambrotype were of ID'd Bayeux family members.