Large Guilloche Sterling Pendant

Hello, 

I've recently bought this pendant. It is gold over sterling silver (unmarked), the large stone is citrine and 2 freshwater pearls and it's really big.At the begining I thought that the enamel part might have been part of a compact or something, but I don't see anything on the back.  I've searched a similar one online, but haven't found anything... any ideas ? Thank you in advance !