An old coin's value can be determined by checking the U.S. Old Coins Identification chart for coins from the United States and the U.S. Coins Red Book for coins that are not on the chart, according to About.com. Coins that are not found on the U.S. Old Coins Identification chart are likely commemorative coins.
In U.S. coin collecting, commemorative coins are defined as special non-circulating coins provided by the U.S. Mint, states About.com. Collectors usually buy these at prices that are significantly above face value, including surcharges that support a program related to the coin's subject. Commemorative coins, particularly non-U.S. coins, commemorate a person, place or event and are typically issued for one year only.
About.com notes that old coins coming from other countries can be identified through the language used on the coin. Generally, if the old coin does not have a country name and denomination, it may not be an official government coin. If it is difficult to determine the origin and value of an old coin, About.com recommends taking the coin to a coin dealer. However, it is important to be careful when selling old coins, as many dealers attempt to buy such coins at prices lower than their real value.