Collectible coins are pieces of currency that are valued for more than their face value due to their rarity, demand, material composition, or historical significance. One prominent example is the American Silver Eagle, which was introduced in 1986 and is made of one troy ounce of .999 fine silver. The 1988 Silver Eagle is notable among collectors due to its status as a key date within the series, with a limited mintage contributing to its desirability. Collectors often seek these coins for investment purposes or to complete specific sets.