Recognize this sulky plow?

I bought a sulky plow recently and am unable to find a brand or name on it. It has a broken part that I need to replace or repair. It would help if I could find out the brand. It’s not in either of Lynn Miller’s books.

There’s no paint left on it. It is a heavy-made plow with heavier wheels than most plows had. All of the casting numbers start with the letter P. It’s missing one spring. The part that throws me off the most is the rod running to the seat bracket. I can’t find any other plows that have that spring. It looks like a P&O in the front but has nothing else to say that’s what it is. I need the furrow wheel adjusting lever and the part that goes with it.