* Condition: The most significant factor. A complete set in pristine condition with the original slipcase and minimal wear will be worth considerably more than a set with damaged books, missing pieces, or significant wear.
* Completeness: A complete set of 20 books is more valuable than an incomplete set.
* Edition: While you specify 1969, there might be slight variations within that year that could affect value.
* Market Demand: The current collector market's interest in this specific set plays a role.
Where to find value estimates:
To get a realistic appraisal, you should check these resources:
* eBay sold listings: Search eBay for completed listings (not active listings) of similar sets. This will give you a good sense of what others have recently paid. Pay close attention to the condition described in the listings.
* Abebooks: This online bookstore often lists rare and collectible books. Search for the specific set and see what prices are listed.
* ThriftBooks and other used booksellers: Check their listings for similar sets to get a sense of current market pricing.
* Professional appraisal: For a definitive valuation, especially if you suspect the set is particularly valuable, consider contacting a professional book appraiser. They can assess the condition and provide a formal appraisal.
Without knowing the condition of *your* specific set, it's impossible to give a precise value. It could range from a few hundred dollars for a worn set to potentially over a thousand dollars for a pristine, complete set in its original slipcase.