All Whitman folders are made of acid-free materials for the protection and storage of your coins. The holes in this folder have a special LOCK-IN feature. But first, a word of caution: always hold a coin by the edge and never touch its obverse or reverse. We recommend you wear gloves when pressing your coins into place. Now that you are ready, simply place the coin with one edge tipped into the hole, and then press the high edge downward and toward the lowered edge (slantwise). Feel the snap? It's locked in! For the collector who wishes to build a collection that is both general and comprehensive, this folder for U.S. Coins of the Twentieth Century contains openings for each type of coin (including major varieties) produced for circulation during the 20th century. Coin types and dates of issue are listed on the inside flap of this folder. A great gift idea for any Coin Collector!