The ruby clasp appears to me to on a 2b strand pearls not 3 strand. I think a longer single strand is added to your pic
--Previous Message-- : : The gift received from the Queen's : grandfather is rather easy to distinguish. : The only triple strand pearl necklace worn : by the Queen as a girl is one made of pearls : that are all nearly the same size. Unlike : the one shown above the pearls are not : graduated. : : As Princess Elizabeth this necklace was worn : frequently and continued to appear during : the early years of the Queen's reign. : : : : : : : : : : : : : : : : : : : : However, I have only been able to find three : photos of the pearls being worn during the : last 50 or so years. : : : Tuvalu, 1982 : : : Golden Wedding portrait by Lord Snowdon, : 1997 : : : Mansion House, December 8, 2009 : : : There appears to rubies in the clasp, which : would match the earrings and bracelet worn : in 2009. : :