The vinegar sounds like a good idea. I know those inlays don't like to be polished, as the swirl/metal-turned finish will dissapear with any kind of harsh metal polish.
The other alternative is to get new inlays. They sell them at CAE sound, and they have almost every one needed for a Mini. A package of 20 sells for $15.00 US. Not sure how easy removing the existing ones would be, but I have seen the stock inlays simply fall off on hot humid days.
Here is a link to CAE:CAE Sound parts page
They seem like nice people that cater to restoring old electronic instruments like Hammonds, Rhodes, ARP's and Moogs. Can order by phone during their regular hours. Not sure how much shipping to Canada would be?
But I don't recommend "polishing your knob".
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