Hi everyone. Please help identify this necklace. It has a Mikimoto box, pouch and booklet looks old. chain is 15 in. Clasp marked with M SIL and Sterling. Bail has an M and S. I cannot find another one like it anywhere so have no idea if it is real or what it may possibly be worth. Pearl is creamy white 7 1/2-8mm, looks pretty round, it is gritty when rubbed against another pearl. Pendant approx 1 1/2in