there might be a bit of apples and pears comparisons here, not sure of my dates ??
Ned's original info was from 1982, the point at which there was simply 531 (the same for both racers or tourists) and 531SL for those who wanted a lighter frame.
Ed's info is later than that, 531SL had been discontinued and 531Comp had been introduced for sporting bikes and 531SuperTourist existed for touring bikes.
So Ned's 531 is not the same as Ed's 531 ... not sure where the MKM ultimate fits, as I'm not au fait with the MKM's age??