This is a rare 52" necklace from Trifari's 1964 Renaissance Collection.
It is often called "stained glass" because of the way the light shines through the open-back glass cabochons.
Trifari called this color "mock rubies" in their advertisement.
I have not been able to find another one that is this length.
This can be worn flapper style, or double or triple strand.
Has Crown Trifari mark