my find from my grandmother

these beautiful pearls were found in my grandmothers wardrobe. I believe they were purchased by my great great aunt whose name appears on the receipt. I am not sure really what I have. They were in a case with the two clasps and the recpt and a booklet that has the story of K.Mikimoto that also says readers digest. I would like to know really what I have. I have had one opinion on a forum. Regardless I think they are beautiful.