I agree with both Rick and Archie. CIC chips can have varying materials in the center, with the most common being stainless steel. They don't rust. The brass center chips will tarnish in time, while the stainless will remain as shiney as the day they were made. B.C. Willis CIC chips are the same. A perfect example would be the large key CIC chips they put out in the 70's for the Carson City Nugget. Even after forty years, they still look great.

The best thing to do with them is simply enjoy them.