use one of the commercial coin dips, that should remove the tarnish and allow its luster to show. Be careful to follow the instructions and avoid overdipping it though.
Just about any of the things you read on these forums of what not to do to clean coins. Most will work to some degree. For just household products, try lemon or lime juice. Tarn-X from a jewlery department from any store like Walmart. Baking soda in water solution with a very lite rub. Actually anything that is sold in the jewlry department of any store for cleaning jewlry. If it is pure silver it will eventually dull so you may want to try spraying it with laquer after you get the shine. By the way, how did you make that?
i did it in a cnc milling machine, i used a x-mas silver round that i picked up for $5 a long time ago,i had to use coolant because the silver is so soft that it will just push and not cut without it, the coolant makes it turn yellow.
