Usually, platinum rings are stamped with either PLAT, PLATINUM, .950 or .900. The stamping that you're referring to normally refers to sterling silver. Unless there is a new strange alloy of platinum that I am unaware of, then the stamp you're looking at is on a piece of sterling silver jewelry.
If you're still unsure, just go to your local jeweler and ask them to test it for you. I found a good tutorial on precious metals, though, that might be helpful. You can read it by clicking on the link underneath this posting. It describes each type of precious metal in depth so you can get a better understanding of each that might allow you to determine what your ring is.
A ring with 925 engraved on it would be made from 92.5% sterling silver, not platinum.
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PLAT engraved on the inside of the ring indicates that the ring is made of Platinum.
Look to see if 925 is engraved inside the ring, if it is it is made from sterling silver.
It means that the Silver was mined in Nevada
A diamond can be mounted on a 925 FAS ring. They typically are mounted however on gold or platinum rings.
i would say platinum
Size 8, maker is NV, 92.5% silver (Sterling silver)
The 925 means that the ring is sterling silver (92.5% silver with 7.5% copper). Not sure about the DQZ2 though. It might be a manufacturer's mark, but I'm not certain.
925 means it's silver
925 indicates the purity of the silver out of a possible 1000. A purity of 925 is fairly standard because they take Fine silver (999) and add a small amount of copper to give it strength and beauty. 925 is more commonly known as "Sterling Silver". A US size 7 ring would be size N½ in Australia, Ireland and the UK.