One of the more interesting pursuits in the coin collecting hobby is called "cherrypicking." Cherrypicking is the art of finding rare die varieties or other coins (i.e., "cherries") at a fraction of their real value because the owner is unaware of their true nature.
Now not everyone agrees with the ethics of cherrypicking. Is it fair, opponents ask, for a collector to walk into a dealer's shop, search through the dealer's inventory and buy a $5 coin that has a value of $50 or $500? Some who object to the reverse - a dealer paying a collector $5 for a $500 coin and not telling the seller that the coin is rarer than he suspects - believe a collector has an obligation to be truthful to a dealer, just as a dealer has an obligation to be truthful to a collector.
Others, however, believe that a dealer, who is in the field as a professional, should know his stock. If he misses a rare die variety because he doesn't have time to closely examine each and every coin he owns for die varieties, or hasn't bothered to learn about die varieties, then it's his own fault that he has improperly identified and priced some of his stock, others say.
Ethical issues aside, lots of collectors and dealers cherrypick. Armed with specific knowledge about varieties, they closely examine coins in dealers' inventories, hoping to find a rare variety, or maybe even a previously unknown variety, such as a doubled die coin not previously reported.
It takes time to learn how to cherrypick. A cherrypicker must look at hundreds and thousands of coins, and must be able to distinguish doubled dies from mechanical-doubled coins; must know what repunched Mint marks look like; must know what series are ripe for the picking. (Want to know more about doubled dies, coins with mechanical doubling and repunched Mint marks and how they happen? Read about them in Errors ... How They Happen, a companion Coin World booklet.)
For those who successfully find cherries, it's great sport. Finding a rare die variety worth several hundreds of dollars for just a few bucks is a wonderful feeling. It makes those hours searching through thousands of coins with no luck all worthwhile. And everyone loves a bargain.