- Edition and printing: Different editions and printings of the Encyclopaedia Britannica may have varying values. Check if you have a first edition or a specific limited edition, as those can be more valuable.
- Completeness: A complete set of the Encyclopaedia Britannica, including all volumes, is more valuable than an incomplete set.
- Condition: The overall condition of the encyclopedias is important. If the volumes are in good condition, with minimal wear and tear, they will retain more value. Damaged, torn, or heavily used encyclopedias will be worth less.
- Demand: The demand for older editions of the Encyclopaedia Britannica can also affect their value. If there is a high demand for vintage encyclopedias, the value may increase.
Since values can fluctuate, it's always a good idea to consult a professional appraiser or check reputable online sources for the most up-to-date market value of your 1990 set of Encyclopaedia Britannica.