The necklace is tied with a single double-back knot between each bead. Then, it's tied-off with a single double-back end-knot (at each end of the clasp). And the clasp is a very typical filigree box clasp.

All of this says "1980."

At that time this was the way new necklaces were presented. I spent a few hours examining and experimenting, to learn these knots. And I teach them in my Bead Stringing Clinic. I was very impressed that a single knot was used to close a necklace—that was strong and didn't unravel itself. The way it's tied, pulling on the cord (from the necklace itself) actually makes the knot tighter, and not prone to untie itself.

In 1980 I had been collecting and examining Chinese necklaces for ten years. But I had never seen this before. Plus, this is the time that filigree box clasps became common in the marketplace (though I understand they existed from before this time too).