Carolyn,
Welcome! Most of us value luster more highly than any other pearl quality, so I'd put your pearls in the outstanding category! In person the blemishes are barely noticeable, I imagine. The clasp is so luxurious looking, no doubt from when gold was much less expensive. Do you know when your Mother purchased or received the pearls? Based on the size and age, if more than 20 years old, they would likely be cultured akoya pearls from Japan.
Twenty four inches is a wonderful length, too. You have a beautiful legacy from your Mother; do you remember her wearing them?