Cleaning silver can be done a few ways. Depending on the object, you can use acetone to make it look like new. Tarnished silver coins can be cleaned using acetone if done correctly. It is recommended you keep silver jewelry away from products with acetone and consult a professional jeweler before experimenting with any cleaners.
Soak any dark silver coins in a container filled with acetone or nail polish remover that contains the ingredient.
Wait until you see the dirt come off the coins and then air dry.
Pat them dry with a soft, clean cloth for faster drying time. With any type of silver you want to be gentle so it doesn't get scratched.