This is a bit gruesome but I'd like other opinions:?

Before my Dad ped away he told me my Grandmother was buried with a very valuable ring. A huge diamond. He told me to get it. That is not something he would just say. If he thought it was very valuable, I'm sure it is. There is the possiblity that it was removed just prior to burial. (Theft) But, I'm thinking if it isn't too far out of line, maybe I'll do it. Your thoughts please.