if its not, someone sure did a fine job of cutting the second plow off. Only one like that i have ever seen.
We have two Ferguson double disc plows, the older one looks just like the one in your picture with a second plow cutoff and the end cap reattached to the frame tube. The other later model MF disc plow has a bend tube frame. Do not know why they did that as both old plows do a fine job.
The key to the proper operation of a Ferguson disc plow is the rear trail disc wheel, in must be in good condition and full dia. As the Ferguson disc plow is much lighter than most old disc plows and the rear disc wheel is what keeps the plow running straight.