I believe I have the sister to that blade. I used it extensively with an 8N 45 years ago when building my house. It pushed a lot of heavy clay. There was a movable yoke type lock for the top 3 pt hitch arms to hold them in place, forcing the hydraulic oil through a normal 2 way hyd valve to either lift or lower the blade. When the blade was up, the yolk could be moved free of the lift arms and then the 3 pt hitch would work normally. So it carried either a 6 ft rear blade or a dirt scoop. Most of the time, I had the bottom clevis end of the 2 way cylinder attached to a short chain and then the blade frame. This gave a float ride to the blade. It sits in my back tree line. I do not have any paper work for it.
Paul in MN