Deco or Repro - Signed "Sterling Vintage"

[natNYC]

This is a frustrating mark, as the name is so vague it's hard to research it.
The piece is a brooch that can be converted to a pendant with a clever hinge mechanism.
The main piece looks like rock crystal.
it has a genuine diamond in the center.

It is marked with a hallmark i can't make out
and then Sterling Vintage.

it is in such good condition, i suspect it is a reproduction.

Any help/insight greatly appreciated.