What does the rest of the clasp look like? The mark is most likely the company that made the clasp, and not the company that strung the necklace. It's only the high end jewelry companies that make their own clasps, and then the clasp itself is very distinctive.
From what I could see in your album, the clasp is a very nice ribbed style with a safety bar designed for pearl necklaces. As others have mentioned, probably the hallmark belongs to the clasp manufacturer, not the designer of the necklace.
The clasp looks like it's trying to look like a Blue Lagoon clasp, but it's not. I still think my comments in my first post are probably correct. The hallmark is from the company that made the clasp, and not the company that strung the pearls.