It's a 75 mm Base Ejecting Round. Approximately WWII era. The nomenclature should be stamped on it somewhere. It was most likely inerted at some point, unless you have the shell casing to go with it. If you do, it could also be a load trainer. Whichever it is, it is in an unfired condition (no scoring on the rotating band).
The ejection tube is capped with a shipping cap (the thing that looks like a big screw head). Inside that would have been explosives. Make sure that it does not contain any. Hopefully someone before you was dumb enough to open it and check. If not, you may want to consider contacting your local bomb squad and request that they X-Ray it.
Side question: Where was this found? I ask because the Delaware area was famous for experimenting with converting all sorts of shells into chem rounds back in the day. A 57 mm AA shell bit one of my friends a few years back with HD gas (shouldn't have been in it).
Edit: I've got a call into my old unit. They are going to get into the pubs and get you an exact nomenclature. Also, I did some digging.. That round looks awfully French to me. But I'll see what the guys come up with.
