Despite its outlawed status as a raw material for chess sets, carved ivory still stands out as some of the most expensive material in the world for chess pieces. Based on a few basic facts about the set, you can fairly easily determine how expensive your set would be to a collector.
Who Made It?
If your set was hand-carved by the House of Staunton, a well-known and respected brand of chess piece makers, it will be worth more to most collectors than a set that was made by an unknown person.
However, if the set was hand-carved by a person with some sort of renown or notoriety, the set might be worth quite a bit to collectors interested in that person.
When Was It Crafted?
A basic rule of thumb for collectors is "the older the pieces, the more they're worth". Chess pieces of any kind surviving for more than 300 years are extremely rare, and the ivory makes them doubly-so.
If you can, find a manufacturer's label or peruse galleries of vintage chess pieces looking for signature designs similar to yours.
For example, a set of legal, hand-carved elephant ivory chess pieces from the mid 1940's were sold for $1830 on the website EBid. The price would have been higher for a similar-quality set from an earlier time period.
In a different vein of the "when was it crafted" category, the type of ivory used can make a difference as well. A set crafted by House of Staunton from 40,000-year-old woolly mammoth ivory can be purchased for between $9,000 to $12,000.
What Shape Are They In?
If your chess pieces are in good shape, like anything else, they'll be worth much more. Chips, cracks, abrasions, discoloration and other aesthetic or structural damage will lower the set's value by a substantial amount.
Take note of any such damages, and report them to any appraisers looking at your set.
Is It A Complete Set?
One of the most important factors any collector will be looking for is the completeness of the set. Due to the extremely lose-able nature of chess pieces, it's highly unlikely that an entire set will have escaped the ravages of time without losing a single soldier.
If you do have the entire set, you're in luck. Your set's value is incomparably higher than if it were missing even a single piece.
Ivory is no longer legal as a material for crafting chess pieces, due to animal-rights activism and the scarcity of ivory due to illegal poaching.
If your buyer sympathizes with the cause of animals rights, or is leery about being in possession of an ivory-carved chess set, your price might be be significantly lower. However, shop around for collectors a little bit and you're sure to find one who is delighted to find such a treasure and will offer you a fair market value for them.
Also, due to the tight restrictions regarding the sale and shipping of ivory, check with local authorities when ordering a chess set from outside your state and definitely when purchasing a set that you can't date. If you discover that a set was carved from elephant ivory within the latter part of the 20th century or even later, contact authorities.