It can be difficult even for a professional to tell exactly what a coin collection is worth. You might look through a coin guide and believe that you will receive a lot of money for your collection, but you will probably find that the prices quoted are retail and you won't get that much when you sell to the retailer or even a collector.
Two publications that may improve your awareness of what you can expect to receive for your collection are:
Auction House Coin Collection Quotes
If you have a collection that is worth over $5,000, you might want to go to an auction house and receive an estimate. These are generally conservative and the actual amount you receive could be more than what is quoted. If you allow the auction of your collection, you will pay a 10% fee to the auction house for their services.
Online Dealer Coin Collection Quotes
If you want to sell your collection to a dealer, there are several online sites where you can obtain quotes. If you sell to a dealer, you won't get the highest amount for your coins, but you can get them sold faster. When you find a dealer online, take the time to speak back and forth to be sure the dealer is experienced in trading and not just looking to make money from you. Check with coin guilds to be certain that the person is representing himself/herself truthfully.
Coin Condition Matters
Have your collection in the best possible condition before you attempt to sell it. If your coins are not slabbed, they might not bring as much. If you have some coins that are rare, you may want to have them professionally graded before trying to sell them. This will ensure that you know their true value.
A Small Collection
Some dealers are specialists who only deal with certain coins, and it may be hard to find those that are interested in a small collection. If you have a small selection, it may be necessary to insure the contents and ship it to a dealer to analyze it and give you a price. If you choose to mail the coins, be sure to insure them for the maximum amount your collection might be worth.
Dealer versus Auction
Selling to a dealer won't bring the highest price possible, but it might be better than an auction where the coins could sell lower than you expect and you still must pay the 10% auction fee off the top. If you talk with several people and still do not feel comfortable with selling your coins, just hold onto them a little longer. Although coins don't usually increase in value like mutual funds, they do generally become worth more over time.
If you present your collection to four or more places that are interested in buying them from you, there could be some variation in all the numbers. Whoever you choose to sell your coins to, be sure they are legitimate, and get your money up front.