I would try soaking them in a pot of boiling water with aluminum foil and baking soda, like this, although I usually do it in the sink, with the same method:
There are several metallic stains and other stains that bleach and lime remover don't remove. Part of the ceramic coat is gone! Any help, please. I'm sure my landlord...
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How to clean coins safely and easily:
https://www.thesprucecrafts.com/clean-coins-safely-768309
are they solid silver?
Try coke a cola.
I would try soaking them in a pot of boiling water with aluminum foil and baking soda, like this, although I usually do it in the sink, with the same method:
https://www.hometalk.com/diy/clean/house/how-to-clean-silver-easily-16689326
How to Clean Silver, Easily!