Victorian Pinchbeck fashion brooch with pink and yellow stone

fashion Victorian pinchbeck which has been 18ct gold plated.
It is much yellower than pinchbeck usually is.
There is a bit of tarnish/ verdigris, I think perfume caused it.
What makes this one a bit different is the 2 layer pink and yellow stone , I have never had an intact one like this before. Glass but very clever.
55x45mm
Circa 1850 ,so in pretty good condition for the age.