Vinegar worked on this Kashi that i bought off Si Zippy. Didn't have any before pices but it was way worse than all the ones you've put on this thread so far. Forgot about it for a week, then 10 mins on the polishing mop - hey fookin presto, here she is....

I only used table vinegar though - I fancy that pickling vinegar would strip anything mind

Spen