First of all, avoid direct bumps and rubs with hard objects. Do not pack several coins in one pocket at the same time, and use soft cloth or paper to wrap them separately.
Secondly, it is necessary to prevent hand contamination. When the challenge coin is shipped from the factory, it comes with a thin, sealed transparent plastic bag to prevent the surface of the coin from being oxidized. Don’t take it out easily and touch it directly with your hands. When viewing the challenge coin, If possible, wear thin gloves and pinch the edge of the challenge coin with your thumb and index finger to prevent sweat stains from contaminating the coin surface.
Again, avoid contact with acidic substances.
Challenge coins should be stored in a ventilated and dry place.