I need a professional opinion about 50+ yr old 1ct? round cushion cut yellow diamond that has been handed down to me. The stone itself was given to my father by my great-grandmother, and he put it in a platinum basket setting and gave it my mother as an engagement ring. I know that she had it appraised before but I need to know if now it is even worth getting it appraised let alone selling it which was what I had in mind of doing. Please help me. Thank you.