I'm afraid I can't help with authentication and have no idea about value but I did want to say what a beautiful clasp and what an informative note your Mother left about the pearls.
I see it was written in 2000, I imagine $1400 was a fair sum to pay for pearls then, and possibly even earlier as...
What a happy Christmas your friends and family must've had with their pearly beauties, each one so special.
Look forward to seeing your 2019 creations!
So elegant and poised! Thank you for hunting and sharing with us.
PS
I enjoy all your threads, BPDDC, thank you, I just don't always log in to comment on the many beautiful and interesting things shared across the forum.