Hi,
It possibly is a one of a kind, hand made by a crafter. Even so, it is one of the nicest of those I have seen. In the 1960s there was a rage for making beaded jewelry at home, using techniques similar to macrame and crochet, and often using metallic threads or yarns. Stores sold a wide variety of these Bead Work jewelry books, and I still have some from my teen years. Choker and wide necklaces were popular in the mid to later 1960s in the books I have seen from that time. There were books with instructions for hippie styles, Victorian styles, and more contemporary styles. Many of the designs were quite intricate. I have never seen one with so many nice quality pearls like yours, it is quite spectacular for that type of thing.
I could, of course, be wrong, but I have seen so many of these over the years, made of gold or silver metallic threads with pearls and other beads, that it really looks like one of those to me.