My friend and I have two of these old plows.
His is a Ferguson like the one in your picture and mine is a later model MF 64 Bent tube, probably one of the last ones they made.
the older ones were called bullet plows because there frames looked like a large bullet, I guess.
They work good, but leave the dirt a little more rough than a regular flat bottom.
They had there place before trip beam plows came out. These old plows would roll over or kick out a root or rock and keep on going, where the non trip plows would hang up or bend a beam, etc:
However, to operate properly, the rear disk guide blade must be in good to very good condition.
If not, it will not guide the plow properly and the plow will pull to the left.
I had to replace the rear guide blades on both of our plows. used new plow coulter blades,
That may be the reason the old plows were set aside, owners did not want to fool with replacing the rear guide blades.
Some say that a Ferguson wrench came with each disc plow and it was stored in that tube, we never opened the end caps to see if a wrench was still inside??? who knows!!!
Just a different twist on plowing, if you have an old fence row or some rough rocky ground you do not want to put you A-1 flat bottom plows in, then buy the old plow and save it from the scrap yard. I would not take that kind of price for mine.