It's called a disc plow, or disc tiller. Ford used to sell them. The 1951 Dearborn Plow brochure I have shows one which looks fairly similar to yours. They called it the Taylor Disc Tiller. They say it's used for terrace building, working in trash, stalks, and stubble, and for turning cover crops. The Taylor disc had four 26" discs spaced 10 inches apart, with a high beam to avoid wadding up of trash, and the furrow wheel at the rear to aid in steering. Also, the high carbon discs are on sealed, opposed, tapered roller bearings riding in an oil bath. 640 lbs. Like a lot of the old equipment of that era it is massively overbuilt - or at least built to last a very long time.