Maybe a spinner plate for a fertilizer spreader truck. Judging from small bolt hole and pattern I dont think its heavy enough to be a cutter of any kind.
Kubota M7040, Kubota MX5100, Deere 790 TLB, Farmall Super C
If you are in a treed area I'd say it could be the wheel off a tree seedling planter. Just a guess but I have seen similar and that's what they were and used for planting and spacing small seedlings.
I can't help with what it used to be but it looks like a perfectly good 700yd target for me. Of course I would have to fill the center hole since that's where my rounds would be going.:laughing: