It looks to me like someone made himself a gardening tool out of available parts. I cannot say what the parts were originally, or when this item was made. I agree the hex nut is "modern" but I have no idea when they came into general use. I'm just speculating that this might be a genuine object that was made for a legitimate purpose (not military) and not necessarily made for fakery. I have no idea about the CSA stamped into the eye piece. That might, indeed, have been done to deceive.
I have come across an amazing bunch of old, cobbled-together tools in barns and sheds around my area in central Missouri. For example, I own an earth tamper that some farmer made from a heavy axle, a steel plate about 8" square, two bolts and nuts, and a heavy steel stirrup-shaped watchamacallit that connects the flat plate to the axle / handle. At least I use it as an earth tamper as I can think of no other use for it. My father had it before me and he probably found it in the barn of the farm he moved our family to just after WWII. He tamped earth with it, too, whenever he needed to pour a little concrete around our place.
My point in all this is that it's an odd and interesting piece and a great conversation starter. Just let your friends and guests speculate about it and enjoy having it. It doesn't have to be a military artifact to be interesting and fun.