Without handling it and seeing it up close, it may indeed be a patent wrench. It also may be part off an older harrow or horse cultivators. I have also seen the part of older patent plows that scrape dirt of the coulters that look kind of like this. If you found it in an old farm field the context might help you. I find parts like this every Spring and Fall when I plow. There were hundreds of different patents for such equipment, and it can be a real puzzle. CH Wendel has written some good books that might help you.