What are some red flags in price guides and online value lists?

Be wary of any source that does not explain where its numbers come from. Values pulled from asking prices, rather than actual sales, can be well above what items really bring. Lists without dates may be years out of date, and values in many categories have shifted over time.

Watch for broad ranges that seem to fit everything, values that ignore condition, and lists that seem designed to sell you something, such as a grading or appraisal service. A source claiming an ordinary item is worth a fortune should prompt a closer look, not excitement.

Good research uses several sources. Compare published values with recent sold results for closely matching items, and pay attention to condition and details like maker's marks, size, and variations. When an item may be valuable, a qualified appraiser or an auctioneer who handles that category can give you a much better sense of real market value.