This is a base to create a fake embroidery brooch for Cersei's coronation gown, which she wears at the back of her neck.
Note that this is NOT a finished product; you will need to paint and add rhinestones or beads to it as well as glue a brooch pin to the backside to make a wearable product from this 3D print.
The material that was used to print the finished version is Frosted Ultra Detail.
I have detailed instruction on how to paint it / add rhinestones on my website here (under "The Embroidery / Brooch").
You don't need to purchase any of the "real metal" printouts to achieve that metallic look; you just need to paint it.