Here's why:
* Condition: The condition of the books is crucial. Are they in pristine shape, or are there tears, stains, missing pages, or general wear and tear?
* Completeness: Is the set complete, or are there missing volumes?
* Rarity: Some special editions or sets with unique features may be more valuable than others.
* Market Demand: The value of any collectible fluctuates based on current demand.
To get a better idea of the value, consider the following:
1. Online Research: Look for similar sets on auction sites (eBay, etc.), online marketplaces (Amazon, etc.), or antique book websites. Pay attention to the condition of the listings and compare their selling prices.
2. Local Antiquarian Bookstores: Visit local antique booksellers or specialized book dealers. They may have experience with antique encyclopedias and can provide a more informed estimate.
3. Appraisals: If you're serious about getting a precise value, consider contacting a professional appraiser specializing in antique books or encyclopedias.
Remember, the value of your set can be influenced by several factors, and a general online search or estimate from a local bookseller may not be completely accurate.