Voluptuous, huge glass beads are the highlight of this Art Deco necklace with French hallmarks. Five marvelous emerald green-and-clear beads in three sizes alternate with smaller lime green beads of the same design, set in sterling silver. I don't know the name of the technique used, but I can see that the glass has been elaborately layered around the bead core. Beads were actively traded around the world during this period, and these are either Italian or Czech. The largest central bead measures nearly 1" by 5/8".
The original portion of the necklace measures 13-1/2", and the previous owner has added a modern chain to each end as an extender to 21-1/2". This new chain has green glass beads and silver tone metal beads, two of which have turned gold.
If I were keeping this necklace, I would replace the extension chain with sterling chain, a fairly low cost option, to maintain the integrity of the original necklace.
The original, hallmarked clasp was saved and re-attached. It has the French boar's head mark, and my tests show the original elements as sterling.