kebo is right; it is a rotary hoe. On south Georgia farms it was used if after planting and before the seeds broke through, the wind dried a crust on the soil. The tines would crack the crust enough to let the seeds break through. Though called a "hoe" , it was not designed to remove weeds.
I liked them because the driver (me) didn't have to pay much attention to what he was doing, you could go pretty fast and generate you own cooling breeze, and they were so easy to pull that you ran all day on a tank of fuel on a John Deere 420.