What does 750 925 mean on jewelry?

Answer 1

These figures generally denote the purity of the metal used for jewelry. I have seen such markings on platinum jewelry. The most common are 850, 900 and 950. These denote 85, 90 and 95% purity. The 750 and 925 markings can also be found on Silver jewelry, denoting silver with 75% and 92.5% purity.

http://www.b2cjewels.com/education/platinumguide.aspx
http://www.b2cjewels.com/education/silverguide.aspx