If the history is correct, and with the photos, I'd say you have a strand of unbranded 6.5mm cultured akoya (saltwater) pearls with a clean surface. They have nice luster, and the length is a plus.
They should be restrung-- silk absorbs skin oils, environmental grime etc. and over the years it becomes dirty and weakened. If it breaks, the necklace may be lost. The knots appear to have gotten dirty over the years. If you are keeping the pearls, you may wish to restring them yourself to save money. See the tutorials stickied on the Lowly Beader's Club. (This is actually not hard to do-- I restring my own all the time.)
As to value-- are you talking about replacement value, or resale value? Replacement value will always be higher. Look at similar strands new online to see what they are selling at, and there is your replacement value.
Resale value is going to be lower.
• Pearls do not tend to hold their value unless they are historic or a well-known and desirable brand like Mikimoto.
• Pearl nacre tends to thin over the years with wear.
• The buyer will have to restring them, which is often $3+ per inch (one person here was quoted $1 per knot).
• Smaller pearls are less in vogue today. The advent of high quality round cultured freshwater pearls has made it more affordable for ladies to buy larger pearls-- and we do!
• If you consign them, you will lose about 50-55% of the sale price to the consignment shop.
• eBay has its fees as well.
You might sell them on Diamond Bistro.
To see what customers are currently paying for a similar strand, check sold items on eBay. But if it were me, I'd restring them and wear them.
