The best place to get third-party information about the value of different coins is to check out the Red Book, which is the official coin pricing book that most collectors and numismatic professionals use. You can buy an up-to-date version of the Red Book online, and it will tell you the market value for hundreds of different rare coins.

One of the problems with the Red Book, though, is that it lists values by grade. Unless you’re a professional, you shouldn’t try to assign your coins a grade on your own. Instead, take your coins to a numismatic professional to have them graded. If you think that the first person to look at your coins isn’t giving you a fair price, you always have the option of getting someone else to double check the grade.

Once you know the grade of your coin and as much information as you can get about the particular coin that you’re trying to buy or sell, you can then double check a dealer’s price quote with the stated price in the Red Book. Although the price you’ve been quoted may vary a little, it shouldn’t be too far off from the listed price for the coin.