Sterling silver which is 925 parts fine silver and 75 parts copper OR Argentium which is 935 parts silver and the rest is a mixture of Germanium and copper. This has a much higher resistance to tarnishing than Sterling silver.
Items under 7.78g do not legally need to be hallmarked but many of my pieces are.
I sometimes use gold as decoration on a silver item, either 9ct, 14ct, 18ct or even 22ct. Details on individual pieces.
To help you translate the markings on a precious metal item see the Goldsmith Hall Dealers notice below.