Jackie - 950 PT is the mark for Platinum. It is white metal with a slight grayish caste and therefore a great choice for platinum engagement rings as the white metal is not only strong but highlights a girl's best friend ;-)
Platinum, iridium, palladium, rhodium, ruthenium and osmiridium are the metals that make up the platinum group.
Platinum is used for luxurious platinum wedding bands. It was seldom used in jewelry until the late 1800's. It is so dense and hard that it was only in the late 1800's that a new torch was invented that was hot enough for the average jewelry to work with on the metal.
Platinum is more expensive than gold. Other marks for platinum are: plat plat 10% irid platinum 950
Concerning the other mark, 900 AU AU is the chemical name for gold and the purity mark for gold from the European member state, Slovenia is marked AU.
The higher the gold composition the more yellow in appearance is the color of the metal. 22ct is a high carat gold and is sometimes marked 916 so 900 would be slightly harder.
The jeweller has used platinum in the ring band not only for its beauty but for its superior strength.
