electrolysis,,,,,,I use an old phone charger,,,,,spit the wires,,,,use alligator clips and clip one to your find and put in a small glass of water with salt,,,,,clip the other to a piece of SS and clip it to the top of the glass in the water,,,,,leave for about 30min or an hour,,,,pull it out and drop on a paper towel with baking soda and rub with your hands,,,,this little silver/gold combo beauty I found recently was black until I put it through,,,,,GL HH