Identifying Blue Lagoon clasp

by Jackie
(Bay Shore NY USA )

I just purchased a 16" strand of pearls from ebay labeled Authentic Akoya Blue Lagoon. They arrived in a Blue Lagoon box with information card. However the clasp is two oyster shells without a small pearl in the center. The back says "BL", under that "585" and under that a small "F". I've been researching on the internet and cannot find a clasp that has an "F" on the back nor two clams shells without the pearl. If these are fake I want to send them back. There is a 14 day return policy. Can you let me know as soon as possible if this clasp sounds authentic? Thank You JS