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Perhaps a little Comet / Ajax type cleanser on a toothbrush or Scotchbrite pad will be aggressive enough to take off the oxidation and flexible enough to get inside that logo....

Best idea I...

9 times out of 10 this is just oxidation on the scales you find this a lot on the older "Slick Black" scales....
A good 3m scotch brite scrubbing will normally get rid of it, for the really bad ones...