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The marking of platinum jewelry is different from other metals. For the USA platinum should be marked according to the Federal Trade Commission guidelines. These are summarised in the table below but more details can be found by clicking on www.ftc.gov/opa/1997/04/platguid.htm.
| Percentages | Common quality marks | Johnson Matthey alloys | Forms available | | 95% platinum | 950 Pt,
950 PLAT
Pt 950
Platinum
PLAT | 95.2% Pt/4.8% Co
95.2% Pt/4.8% Ir
95.2% Pt/4.8% Ru | Chopped rod (grain)
Ring tube
Thin wall tube
Wire
Plate | | 90% platinum | 900 Pt
900 Plat
Pt 900
IRIDPLAT
10%IridPlatinum | 90% Pt/10% Ir | Chopped rod (grain)
Wire
Plate | | 85% platinum | 850 Pt
850 Plat
Pt 850 | 85.2% Pt/15% Ir | Wire | | Between 85% and 50% Platinum should be marked with appropriate marks of the major metal constituents. | e.g.
585Pt 365Pd
585PLAT365PALL | | |
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