I haven't previously seen one which is absolutely EXACTLY like it (because part of it seems to be missing)... so I can only give you my "best guess." It very closely resembles an 1870s-to-1890s Breechloading artillery projectile. If so, it is missing its copperbrass sabot (a.k.a. "driving band"), which fit into the wide shallow recess encircling the middle of the its body. The lack of even tiny evidence of the presence of a fuze in its nose or in its flat base indicates it is a Solid-Shot (non-explosive) projectile. It MIGHT be a 37mm Hotchkiss Solid-Shot (third projectile from the left) in the photo below. Of course, the one in the photo, being unfired, still has its wide copperbrass sabot, and is still in its brass powder-casing.
We need super-precise measurement of your projectile's diameter, in hundredths-of-an-inch) to figure out what caliber it is. If it's about 1.43-inches, it is a 37mm-caliber artillery projectile.