Currency Wiki
Coin holders

Different coin holders.

A coin holder is typically an air-tight object used for storing coins and preventing a coin's exposure to air and damage. Many times, commercial holders are composed of cardboard or plastic, but some providers offer holders made of polystyrene. Some collectors use plastic ziplock bags or cardboard envelopes for storing their coins, though these methods are considered less safe than using a coin holder, coin case, or coin slab (such as those by the PCGS).