Please help date this necklace...

[innormaltime]

I have had this estate piece for between 15 and 20 years. I am trouble finding out how old it is. It is 30.5 inches long. The piece appears to have been black japanned. The clasp looks artisan made. It is a pronged cup setting and stones might be AB rhinestones (it needs to be cleaned). I can't find anything similar in one strand. Looks art deco, but I can't find an age for cup settings coming into use. Any help would be great!

[prettywoman-2012]

It is really hard to tell from your pictures as they are rather dark, but custume jewelry in similar style was made around the late 1940s and up around the late 1960s for sure, so I would put it at the mid 20th century.  I hope this helps. 

PW