Man, I could sort a years worth of brass in that baby!!
As an aside, my vote would be for some sort of crop separator /washing device. Maybe cleaning and sorting freshly harvested potatoes or cranberry's? Despite the rust, it is missing the tell tail signs of denting, bending and general hard use that sifting dirt/rocks would produce.
Lookup at the trees/land around it, the area seems to have been cleared not much more than 50 years or so ago.