score:8
Your piece is from a creator by the name Gilles or Guy Vidal.
You can find several pieces for sale around the web, with one, Poppy' Vintage Clothing selling an item labelled as
GILLES GUY VIDAL BRUTALIST SUN PENDANT NECKLACE MODERNIST ABSTRACT PEWTER 1960S
This page shows a good picture of the backside with the makers mark, a gv:
Another site, a silver discussion forum, the Silver Salon Forums, had a question concerning your mark here. The response mentions that the jeweler used an alloy of pewter and sterling , worked predominately in the 60s and 70s, and was out of Montreal Canada.