Mysterious Necklace with Deco-era Chinese Cloisonne Beads

Etsy shop MaisonettedeMadness has on offer an unusual necklace featuring Chinese cloisonne beads.

The necklace is described as 30 inches in length, with cloisonne beads measuring approximately 22x17mm, caged white metal beads 19x12.7mm. "Round almost black beads are stone or a Peking style glass, clasp is stamped sterling and the chain throughout is sterling silver, the metal wires are all silver in color, may vary in composition. The wire wrapped could be better."

The stamped chain, beads, bead caps and clasp seem almost certainly to be of European or U.S. manufacture.  The black beads seem to have been made to imitate black pearls, and may have some sort of coating?  The Japanese, of course, made excellent hand-wound glass beads to imitate pearls.  Could these be Japanese glass?  Or are they in fact stone?

The cloisonne beads, however, seem almost certainly to date from the 1920s-40s (remembering always the 7-year hiatus for the War with Japan and World War II).  Similar beads can be seen in costume jewelry such as shown in these previous essays here:

http://www.beadiste.com/2014/02/puzzling-evidence-chinese-cloisonne.html
http://www.beadiste.com/2015/07/puzzling-evidence-deco-chinese-charm.html

Maisonette speculates that the necklace perhaps was originally sold in one of Helen Burton's shops.  The necklaces that seem likely to be traceable to Helen, however, feature Chinese findings and metal beads, such as the set featured at the start of this post:

http://www.beadiste.com/2013/11/puzzling-evidence-helen-burton.html


A biography of Helen by Don Menzies can be found here:
http://www.weihsien-paintings.org/DonMenzi/HelenBurton/My_Helen_Burton_Story.pdf

The Miriam Haskell workshop is another possibility, as many unsigned Deco-necklaces attributed to her feature a variety of Chinese and Japanese beads:
http://www.beadiste.com/2013/11/puzzling-evidence-miriam-haskell-mystery.html

Haskell seemed to favor gold-toned brass findings, however, so the silver-toned cast filigree beads in the necklace perhaps originate in the Rice-Weiner workshop, known for its ability to cast intricate designs in pot metal:
http://www.beadiste.com/2013/11/puzzling-evidence-louis-c-mark-rice.html

European workshops also used Deco-era Chinese cloisonne beads, as this bracelet with what appear to be Czech findings and pressed glass illustrates:

Findings are cast brass, with old-fashioned "petal" beadcaps.

Where and when was this elegant necklace put together?  Were all the components sourced at the same time, such as during the late 1940s or 1950s?  Or was it assembled from disparate parts in a later decade?  Puzzling evidence.

UPDATE: Does anyone besides me see a similarity in the cast filigree work in these Deco-era bracelets to the design of the metal beads in the necklace?  Note the Deco design motifs along the edges of the beads.  Evidence that the necklace could date to the 1920s or 1930s?