Ferguson 793 - 3 Furrow Plough

I would guess its age as early 1960's Later 2 furrow ploughs had the long strut as extra support and I would imagine it would be essential on the 3 furrow.

I think a furrow wheel was optional on earlier ploughs, early versions had a flat spring on the wheel which tended to break, the coil spring is as you say because it is a later model. The discs are known as single arm coulter. According to my copy of the handbook they are optional (probably standard on later ploughs) and are better for burying trash.

Yes you could remove the third furrow but you would need to transfer the landslide & furrow wheel to what is currently the 2nd furrow.

My handbook shows a picture of a 5 furrow version though I have never seen one.

Nice plough. The plate shows Massey Harris Ferguson. If I remember correctly MHF was created in 1954 and changed to MF in 1957. So the plough must be between those dates (I guess!)

As said it's a later version