Original CDV, looks like infantry insignia with a 13 (possibly a 15). The back is blank but most of the photos in the album this was found in were taken by New York or Philadelphia studios. I've been told that a potential ID is Lieut. Ralph Tunstall Wood, 13th NY Volunteer Infantry, Co. B.
CDV is 4" x 2.5", very good or better antique condition, clean, blank back.
Shipping: Choice between Ground Advantage photo mailer or boxed Priority Mail.