Farm equipment / plow wrench maybe Acme or John Deere if your lucky. The relic hunters will know this one..probably need the markings if you can see them.
Farmers Type S Wrench is what I found. Bottom of photo seems to match pretty good.
I've found a few of these in the farm fields over the years as well.
My understanding is these wrenches were part of a set of tools the farmer often carried into the fields to service their plows with.
Dave