Thank you Dan of Oakville, Ontario (wow, that is far away as I am in Brisbane, Australia) for your kind advice - my Hub is a SRC5 (W) 5-speed. The indicator rod/chain has a blue mark and came supplied with the hub, as did the guide nut (with viewing holes) so must be the correct ones.
Disregarding the blue mark, is there a 'trial-and-error' method to achieve the correct setting? I find that if I get 2nd and 3rd gear right, then 4th and 5th don't engage properly.