I picked ours up along the road a few years ago. It appears to have been a propane or water tank with the ends cut off, and filled with concrete except for a central core/axle composed of a 1.5" steel or black iron pipe. It weighs a couple of hundred pounds and is pulled by a frame of galvanized pipe that extends through the center to a handle like one of the really simple simple wire cheese slicers, like an inverted "Y".
We hook it to our tractor using a trailer hitch accessory that has a clevis on it, and it works pretty well on fresh gravel or softish ground. It does scuff a bit pn turns, but seems none the worse for the wear from it, and it doesn't seem to damage the grass.
Thomas
PS: Welcome to TBN!