A while ago, Jane and I found a pound coin in the soil of our garden. The date on it was 1984 so it was probably lost well before we moved in. The patterns on the coin were clear but it was discoloured to a dark, dull brown colour which spit and polish couldn’t clear up.
We left in a small dish of vinegar for about a week, which lightened the colour a bit but didn’t go much further in restoring it. We then replaced the vinegar with ordinary tomato ketchup…
Within a couple of hours, the ketchup surrounding the coin had turned green and the discolouration was lighter. We rinsed and repeated and the next day the original colour was almost restored. It’s amazing how powerful ketchup is as a cleaning agent. The only thing is, what does it do to your insides when you eat it!