Definitely a CSA .69-caliber Nessler Pattern, which used to be called a CS Shotgun-slug or CS "Elephant Slug." Now known to have been manufactured ONLY at the North Carolina Institute For The Deaf, Dumb, & Blind, during 1861-62, in Raleigh NC. Several variations of its single ring are known to exist. See bullets #191A, B, and C in the book "A Handbook of Civil war Bullets & Cartridges" by James E. Thomas & Dean S. Thomas. The NCIDD&B as sole manufacturer info is given in "Roundball To Rimfire: A History of Civil War Small Arms Ammunition - Part 4", by Dean S. Thomas.