quite an impressive ring! The stone must be precisely cut, aligned with the vertical axis to effect a six rayed star like the star stone in your 20th century ring. Such star stones, (there are also star rubies) can be Natural or Synthetic gemstones. Synthetic star corundums were first produced in 1926. Synthetic star corundums show strongly defined asterism.
Concerning the metal, Platinum was used extensively from the 1920s. White gold was used from 1915, white gold being an alloy of pure gold, with white metals such as palladium, nickel or silver or a mixture of metals.
Platinum has a greater heft than gold or silver and has a grayish caste. Your local jeweler would be able to determine.
