I can't tell you much without an exact measurement of the diameter (inch and metric) at the widest point. What I can tell you is it's a fired solid shot round, and the hole in the bottom is from a tracer element which has burned out. It's not dangerous unless you drop it on your toe. The rotater bands are gone, most likely sheared off on impact. My feeling from comparing it to the ruler is that it's a 37mm anti tank round.