Bob
They both can be used for a Norton. I believe the one on the right is for later bikes- 74-75 and left one for earlier bikes. I am not sure the exact year when they switched.
If you are going to use end mirrors off the handlebars then I would use the later model, as it does not interfere with the clutch lever when it is squeezed. take a look at my avitar and you will see what I mean. I found that out when I put my mirrors on the European bars of another earlier Commando. Moving the earlier version up the bar away from the handle grip would look kind of weird. If you are using a stock Norton mirror where it goes through the hole in the bracket then either will work.
Cheers,
Thomas
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