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The oldest and most common jewelry alloy for platinum is 90% platinum, 10% iridium. You'll see various stamps, the most common maybe is 10% Ir Plat or something like that. Occasionally it's all spelled out, too. A newer alloy is 950 platinum, where the other 50 is usually cobalt. Usually that is stamped 950 Plat. or 950 Platinum. Those are the two most common, anyway.

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17y ago

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