The value of old coins varies with current demand and the maximum amount collectors are willing to pay for them. Metal prices may also be a factor. Some price guides have been established that are widely used by collectors, such as the Professional Coin Grading Service (PCGS) guide.
Some other commonly used price guides include the NGC U.S. Coin Price Guide and the Official Red Book. The closing amount of recent auctions is often a major factor in determining the current price of a particular coin, and price guides that are issued in monthly or yearly installments sometimes list recent auction results.