First and foremost, research the reputation of the seller. This should go without saying, but eager buyers continue to be ripped off by a few people who are eager to dump their cleaned and damaged junk onto the unsuspecting, despite having been called on it multiple times by former customers. Most auction sites have the ability to review sellers and to read other buyers’ reviews.
Secondly, read and understand the seller’s return policy. If the coin in hand does not look like the coin in the photographs online, what can be done to rectify it? Will you get a full refund? Who pays shipping costs?
Thirdly, closely examine the photos of the coin. Photos should be straight on, not at an angle. Some sellers hide hairlines (signs of cleaning) and other problems by shooting the photograph at a sharp angle, causing the light to reflect differently and the hairlines not to show. You could request a different photograph from the seller, or you could simply move on to the next coin.
Fourthly, consider that many rare, or “key,” coins are being counterfeited in large numbers, mostly in China. It is a problem as old as money itself, and online auction sites are rife with counterfeits. Inexperienced numismatists can get excited over the cheap 1916-D mercury dime and think they’ve scored an auction win, only to send it off for grading and have it returned as a counterfeit. Therefore, as a rule, when buying key coins, only buy those certified and encapsulated by a reputable third party grader.
Lastly, avoid online coin sellers who claim they do not know anything about the coin, or coins in general, or are merely settling an estate. As a rule of thumb, these people do know, in fact, something about coins and use ignorance to create a layer of plausible deniability for when their problem coins are discovered.
