The postwar Norton SV s have certainly come in from the cold......Go back to the early 70s,and you could not give one away......literally...and I tried....As a teen ,I remember the local council had a fleet of big4s with the upright"tombstone" boxes.Horrible things ,with long gear pedals,and outside linkages...The "rat gang " had them ,sidecars filled with foxterriers waiting for the chase.And the mosquito spraying gangs also had them......Which brings us to the early SA gearbox......at that time,you could buy a new ex WD Norton gearbox for 2 quid.....So to fit a SA would be unusual,but maybe the owner didnt want to spend 2 quid,maybe he didnt have it......Back to the present and 2 has turned into 700,which is what I see asked for WD boxes now......but the SA box was also fitted to B/S bikes,so what is it worth now.......10% of what a B/S is worth.....Could be sitting on a goldmine.......Incidentally,the Norton boxes were made almost entirely by sub contractors during WW2,as Burmans were pressed making 1/4 million CPs,and also making the precision gearing for A/A sights,not to mention steering gears.