Looks like a WWI 3" HE shell to me, hard to tell from the picture.
I had someone give me a 75MM tank round (live HE) a couple of years ago. The idiots who gave it to me had put it in a vise and drilled holes in the brass case to empty the powder out and pryed the primer out with a chisel thinking it would be deactive after that. He played around with it and had it displayed above his fireplace for years. I had EOD come by my house to check it out. Turns out the warhead was 100% live HE. They went to put it in the back of thier truck and showed me the last thing they picked up. It was a live bangalor mine. It was bent in almost in half at several places. I don't know how that one didn't go off. As I have stated before, never trust any of this stuff and treat it like it's live. There was tons of this stuff brought back by combat vets who were used to it thinking it would be pretty cool to show their friends. It's turning up everywhere now as they are dying off.