Pd is the chemical symbol of metallic palladium, just as gold is Au, silver is Ag, and Pt refers to platinum. 999,990,950 represents one thousandth of the contained metal, for example, Pd999 represents palladium with a palladium content of not less than 999; Pd999 is a jewelry symbol. You should find this mark on the necklace buckle, and there should be a tag (that is, a label) with the quality and logo of the jewelry you bought (Pd999). However, the latest national standard (which has not yet been implemented, and will be implemented on 1 1 month), the word "palladium" should be added to the label in the future to indicate Chinese. Palladium is a popular precious metal recently, belonging to the platinum group, but not as expensive as platinum.