PT stands for precious metal, and generally PT950 is what we call platinum.
In addition, the purity of PT900 is not as high as that of 950, and the natural price is lower.
There are many jewelry brands that cooperate with Platinum Association.
For example: Xie Ruilin, the old temple of Chow Tai Fook. . . many
They all launch their own advertisements, which are called advertising funds.
You can check it in Platinum Association official website.