* Condition: The condition of the books is paramount. Are they in pristine shape, with no tears, stains, or wear? Are they bound in the original covers? Even slight wear can significantly impact value.
* Completeness: Is it a full set? Missing volumes drastically reduce value.
* Rarity: While the 1928 edition is older, it's not necessarily rare. Some editions from other years are more sought after.
* Demand: Market demand for antique encyclopedias can fluctuate. There may be a specific interest in a certain year or topic that influences value.
Where to Find Value Estimates:
1. Antique Book Dealers: Reach out to local antique book dealers or online sellers specializing in rare books. They can provide more accurate estimates based on your specific set.
2. Auction Websites: Check sites like eBay, LiveAuctioneers, or Invaluable for completed sales of similar editions.
3. Book Collectors' Forums: Online communities for book collectors may have knowledgeable members who can offer advice.
Remember: Be realistic about the value. Older encyclopedias, while historically interesting, are not typically considered highly valuable unless they are in exceptional condition and rare.