Value-- I think of 3 kinds: sentimental value, replacement value, and resale value.
I'm sure the pearls have great
sentimental value-- that is often the greatest value of inherited pearls.
We cannot tell you the current
replacement value (i.e. for insurance purposes). To do that you would have to see an appraiser again, and pay their fee. But I don't recommend that; it is unlikely that pearls appraised at $500 in the early 1990s would need to be insured. Also, graduated akoya necklaces are not really the current style so it's not so easy to know what it would cost to replace them.
I will tell you that in general, pearls do not retain value for resale purposes (if you are thinking of selling.)
Resale value is always less than replacement value. Also, if you are thinking of selling them, be aware that if they need to be restrung (very likely), any potential buyers would factor that cost into what they would be willing to pay for them. To pay to have them restrung just to sell them is probably not such a good idea. Restringing can be expensive; many of us do our own restringing, and if that is what you would like to do (whether to sell or keep them), I have a tutorial on how to do that!
How to string (or restring) your pearls on doubled Pattye's Serafil, Beaders Secret, and Power Pro
This is not hard-- really! It is harder to describe it than to do it. Anyone can learn to string their own pearls!
If after reading through this, it sounds too daunting, I suggest making a mini-strand for practice first. Make one 12-15 pearls long just so you can practice how to knot the end 3 pearls on each side and attach the clasps; the middle pearls are easy to knot.
To just practice knotting (without bothering with clasps), make an overhand knot, string on a pearl (or...
If you would like us to look at your pearls (we always like to see pearls!

) you can upload photos using the photo icon on the toolbar -- when you click on it it will look like this, and you can drag and drop a photo into the box:
View attachment 473785
Finally, if selling them is your goal, I suggest you do a search on eBay for recently SOLD, similar necklaces. That will give you an idea of what you might get for them. I think this is a good reality check; pre-owned pearls don't sell for much money unless they were owned by someone famous or are Mikimoto brand (in which case the pearls should have a Mikimoto clasp at least, and preferably also documents or the brand name box.)