Tokens70, you (and Ffuries/Mike) are correct. It is what most diggers and bullet-collectors call a Sharps Ringtail bullet ...although it is technically known as a tie-ring base Sharps. Specifically, it is the 1858-pattern bullet for the Sharps Breechloading Rifle and Carbine. It is bullet #180 in the McKee-&-Mason book on civil war bullets.