Foil-backed jewellery question

The stick pin appears gold, the (closed) setting is silver, and I believe the stone is quartz or glass with a colored foil backing. It was sold to me as Georgian. I have 2 questions:

1.) Is it possible to identify a time frame for this item more precisely? "Georgian" is a long time!

2.) Is there a reason that the setting would be silver if the pin itself is gold?

Thank you!