The Federal Trade Commission’s Guide for the Jewelry, Precious Metals and Pewter Industries

FTC writes:

23.7 Misuse of the words "platinum," "iridium," "palladium," "ruthenium," "rhodium," and "osmium."

(a) It is unfair or deceptive to use the words "platinum," "iridium," "palladium," "ruthenium," "rhodium," and "osmium," or any abbreviation to mark or describe all or part of an industry product if such marking or description misrepresents the product’s true composition. The Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium.

(b) The following are examples of markings or descriptions that may be misleading:
(1) Use of the word "Platinum" or any abbreviation, without qualification, to describe all or part of an industry product that is not composed throughout of 950 parts per thousand pure Platinum.

(2) Use of the word "Platinum" or any abbreviation accompanied by a number indicating the parts per thousand of pure Platinum contained in the product without mention of the number of parts per thousand of other PGM contained in the product, to describe all or part of an industry product that is not composed throughout of at least 850 parts per thousand pure platinum, for example,"600Plat."

(3) Use of the word "Platinum" or any abbreviation thereof, to mark or describe any product that is not composed throughout of at least 500 parts per thousand pure Platinum.

(c) The following are examples of markings and descriptions that are not considered unfair or deceptive:
(1) The following abbreviations for each of the PGM may be used for quality marks on articles: "Plat." or "Pt." for Platinum; "Irid." or "Ir." for Iridium; "Pall." or "Pd." for Palladium; "Ruth." or "Ru." for Ruthenium; "Rhod." or "Rh." for Rhodium; and "Osmi." or "Os." for Osmium.

(2) An industry product consisting of at least 950 parts per thousand pure Platinum may be marked or described as "Platinum."

(3) An industry product consisting of 850 parts per thousand pure Platinum, 900 parts per thousand pure Platinum, or 950 parts per thousand pure Platinum may be marked "Platinum," provided that the Platinum marking is preceded by a number indicating the amount in parts per thousand of pure Platinum (for industry products consisting of 950 parts per thousand pure Platinum, the marking described in § 23.7(b)(2) above is also appropriate). Thus, the following markings may be used: "950Pt.," "950Plat.," "900Pt.," "900Plat.," "850Pt.," or "850Plat."

(4) An industry product consisting of at least 950 parts per thousand PGM, and of at least 500 parts per thousand pure Platinum, may be marked "Platinum," provided that the mark of each PGM constituent is preceded by a number indicating the amount in parts per thousand of each PGM, as for example, "600Pt.350Ir.," "600Plat.350Irid.," or "550Pt.350Pd.50Ir.," "550Plat.350Pall.50Irid."

Note to 23.7: Exemptions recognized in the assay of platinum industry products are listed in the Appendix.

More info @ http://www.ftc.gov/bcp/guides/jewel-gd.htm