Digital gold testing equipment can determine the gold content or your local jeweller can acid test. Platinum was popular during the art deco period. Platinum is heavy, dense and hard. It is white in color with a grayish caste. Marks for platinum include:
plat
plat 10% irid
950
platinum
The marks on the ring tell you the metal is made of gold and platinum. Platinum diamond setting most likely.
The diamond sounds gorgeous! A Hexagonal brilliant cut diamond is a diamond having a crown and a pavilion, spaced by a girdle, and has an overall hexagon configuration, which is the signature of the stone. Facets are cut in the crown of the stone defining an hexagon table and an hexagram in the crown.