Is Pt900 the same as PT900?

Yes. Pt900, PT900, 900Pt, Plat900 all denote the same material — 90.0% platinum. Different markets and eras stamp it differently, but the purity is identical.

How much is Pt900 worth?

Its melt value is the platinum spot price × 0.900 × the weight in grams. Buyers then deduct roughly 5–15% for refining and margin, so a quoted buy-back price sits a little below that theoretical figure.

How do I confirm a Pt900 stamp is genuine?

Look at the mark under 10× magnification for crisp, even strikes, cross-check the weight-to-volume ratio against the expected density (20.1 g/cm³ for this alloy), scan it with the Jewelry Identifier app, and — when it matters — have an XRF test done by an assay office or gemological lab.

* Platinum hallmark

The Pt900 hallmark: meaning, purity & value

90% platinum. Common in Japanese bridal jewelry as a slightly more affordable alternative to Pt950, and in US production where harder alloys are preferred for prong durability.

Published May 30, 2026

Quick facts

Metal: Platinum
Purity: 90.0%
Fineness: 900/1000
Common regions: Japan, international
Density: 20.1 g/cm³
Melting point: 1745 °C
Standard: ISO 9202

Stamps that mean the same thing

This purity may be struck into jewelry as any of: Pt900 / PT900 / 900Pt / Plat900. The mark differs by country and era, but the metal content is identical.

What Pt900 tells you

90% platinum. Common in Japanese bridal jewelry as a slightly more affordable alternative to Pt950, and in US production where harder alloys are preferred for prong durability.

How to value it

The melt value of a Pt900 piece is platinum spot price × 0.900 × weight (g). A buyer typically deducts 5–15% for assay, refining, and margin, so the cash offer lands just under that figure. Stones and complex settings are usually excluded from the metal weight.

How to check it yourself

Examine the stamp under a 10× loupe — genuine marks are crisp and evenly struck, not doubled or smeared.
Confirm the mark reads Pt900 or an equivalent such as PT900.
Weigh the piece and estimate its volume — the density should land near 20.1 g/cm³ for this alloy.
Photograph it in the Jewelry Identifier app to read the metal, hallmark, and any gemstones from the image.
For a binding result, have an assay office or gemological lab run an XRF purity test.

Sources

Platinum Guild International specifications
Wikidata Q880

* Frequently asked

FAQ

Q. Is Pt900 the same as PT900?: A. Yes. Pt900, PT900, 900Pt, Plat900 all denote the same material — 90.0% platinum. Different markets and eras stamp it differently, but the purity is identical.
Q. How much is Pt900 worth?: A. Its melt value is the platinum spot price × 0.900 × the weight in grams. Buyers then deduct roughly 5–15% for refining and margin, so a quoted buy-back price sits a little below that theoretical figure.
Q. How do I confirm a Pt900 stamp is genuine?: A. Look at the mark under 10× magnification for crisp, even strikes, cross-check the weight-to-volume ratio against the expected density (20.1 g/cm³ for this alloy), scan it with the Jewelry Identifier app, and — when it matters — have an XRF test done by an assay office or gemological lab.

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