Thanks Paul, I hope fellow WNG owners are finding the posts interesting
I have been thinking about what to do with the 'plated' parts such as kickstart, gear lever, handlebar levers, pushrod tubes. The period photos of what appear to be 'newish' bikes show these had a 'matt' silver coloured finish i.e they were not painted (although they probably did get painted later on in service).
Here is an example
I have read that the two possibilities were dull chrome and cadmium. I found remains of the original dull silver 'coating' on a few of the parts, especially the choke lever bracket which had survived almost totally intact and on the pivot end of the kickstart. I tested to see if it could be removed with acid (cadmium, like Zinc plating' is easily stripped with acid) and found it had no effect. So it appears that the original plating would have been 'dull chrome'.
There is no DIY 'dull chrome' plating kit available so I have Zinc plated the parts and then dulled the finish with a very fine and well worn scotchbrite pad which was enough to take the shine off. The Zinc plate will also dull/oxidise in a few days as it has not been passivated yet (a dip that protects the Zinc coating). Once it has dulled a bit more I will then passivate so they don't oxidise any further
Here are examples of what I started with, they had medium surface corrosion/pitting which was removed with a combination of a flap wheel on the angle grinder to remove the worst and then 250 grit emery cloth wrapped around a soft wheel on the bench grinder followed by a fine scotchbrite wheel on the bench grinder. There was no need to polish them up as I was after a dull finish.
In the last photo the choke lever bracket is the 'origional' dull chrome finish so I think the Zinc plating is a pretty good match