The unpredictability of market values has been dramatized in recent years by the frequent ups and downs of precious metal prices. Gold, silver and platinum all have trended significantly higher in long-range terms - but all have experienced corrections that have caused their bullion value, and that of bullion-sensitive coins struck from these metals, to fall sharply in the short run. Similar changes can, and have, also occurred over the years with numismatic coins - those whose value is based more on their collectibility.
Price guide publishers generally strive to be as accurate as possible. But the time lag between the preparation of these guides and their publication and distribution can be a matter of weeks - even months. Indeed, the valuations in the best-known guide book - the perennially best-selling "Red Book" - are "updated" months before the release of each annual edition. Yet, for marketing purposes, the cover date of each edition is advanced to suggest that the prices are not only timely but somehow ahead of the curve. Thus, the current Red Book contains valuations compiled in the prior year. This extends its shelf life at bookstores by making it seem more timely than it is, but there's nothing such tricks of the trade can do to keep the values fresh, especially for more volatile coins, which often include the most valuable ones. The "Red Book" even states "the coin market is so active in some categories that values can easily change during that period." One tip for determining freshness of a guide is to look for the precious metals prices and compare them to current prices.
Because they are published more frequently, newspapers and magazines can update their lists of market valuations more often than annual books and presumably keep them more accurate. But price guide sections of hobby periodicals still must be compiled weeks or even months prior to the date the publications reach their readers. Thus, they're unlikely to reflect significant market adjustments - what might occur, for instance, with gold and silver-sensitive coins if precious metals surge or plummet in value. And since a comprehensive guide might include upwards of 10,000 separate valuations, the logistics of regular updates can be daunting for the limited staffs of the major coin periodicals and websites. I have seen needed price changes take up to twelve months to be implemented.
Lag time and logistics aside, errors are bound to occur in the compilation of even the most carefully researched price guide. Recently, for instance, one monthly price guide showed the 1904 Liberty double eagle - the most common "Lib $20" in the entire series - worth 40 percent more in Mint State-63 condition than scarcer dates in the same MS-63 grade. The editor responsible for this price guide was notified of the mistake, but many months were likely to pass before the corrected value would reach readers. In the meantime people using this guide might easily make a disadvantageous buying or selling decision based upon the incorrect information.
Granted, this example was an isolated case. On the whole, price guides can be useful in at least establishing the relative values of different coins within a particular group or given series - in showing which $5 Indians are most valuable and rarer for instance than the most common 1909-D. But collectors should be aware that most of the prices shown in these guides pertain to typical specimens and are apt to be too low - or too high - for coins that are among the best, or worst, examples in their grade level. Also, they should keep in mind that mint state and proof coins generally require third-party certification in the current marketplace, and reputable price guides almost always provide valuations for these coins based on grades assigned by either PCGS or NGC. Typically, coins graded by lesser services are discounted in the marketplace - sometimes heavily - because they are less accurate and less acceptable to experienced buyers and sellers.