It was looking like it might be a (yankee) Parrott shell fragment until I got down to your photo showing the fuzehole... which is too short to be a Parrott. So my "best guess" at the moment is a (yankee) 3" Schenkl Case-Shot frag. But if you'd like me to do more than guess...
Please knock some rust-crust off the fuzehole's "top" and inside it. Then post some well-focused closeup photos, including a "sideview", and measure the frag's length.