Beautiful Retro Blue Green Rhinestone Silver 19" Necklace, Prong Set Square order Stones, Picture Framed, Prong Set w/ Open Back Bezels, Re-Clasp?

This is a necklace that has me guessing....It looks antique; however, the clasp looks new. I do not know if it is old, and the clasp was just added? You can see that all the stones are prong set against silver open bezels, with the exception of the opposing clasp side end stone, which is in a box order mount, which creates more of a greener color on the stone. (See second to last photo). The lobster clasp is marked 925 for sterling silver, but I cannot see any marks anywhere else, so I cannot guarantee that the rest is sterling silver, but it looks like it. This necklace measures 19" long and the framed rhinestones measure 1/4" by 1/4". The total weight is 14.6 grams. Very beautiful necklace with a little mystery to it!