Rotary was a Oildraulic manufacturer around the late 30's or early 40's. Some controller companies used red/green for line and common (not necessarily ground). Rotary was bought out or changed to Dover sometime in the 40's or 50's. The P-56 was the valve at that time. I remember seeing it in the Dover Repair manual. Dover always called there system Oildraulic instead of hydraulic because the medium was oil and not water. I have worked on a number of 56's and you are right that they are fairly simple. The problem is the Liability that you take on when you are not licensed to work on that equipment and the general public (idiots) are using the conveyance. That was my disclaimer... A good machine shop is a blessing.
