MK markings on pearl strand

by RENEE FORTAIN
(NY, NY, USA)

Hello, I have a strand of pearls with a bow clasp and a hallmark MK, it is also stamped 750. My understanding is that this a from a lower line of Mikimoto, that was only around for a few years. Similar to Blue Laggon or Sea Magic but much shorter lived. Have you ever heard of the MK mark?

Thanks so much for any insight!!!