Unbranded cultured akoya pearls. Some pearls near the bottom in that 3rd photo, have the egg shaped appearance that is typical of freshwaters, but I think that is just distortion from the camera.
The quality is average (I'm looking at surface characteristics and luster).
Generic 14K gold clasp; we can't know the brand of pearls from a generic clasp. Most pearls are not a specific brand.
They appear to be a cream color, which is not the most popular color right now (whiter pearls are generally preferred these days.) From the color they could be from before the 1990s. But not very old, as the strand is a uniform size. Graduated pearl necklaces were more common in the 1940s and '50s.
As to value, used pearls do not tend to hold their value, and these were only average pearls to begin with. Look on eBay for similar necklaces that have actually sold, to see what people seem to be willing to pay for them these days-- that is your best estimate of value.