* Platinum hallmark
The Pt850 hallmark: meaning, purity & value
85% platinum. Used in chains and pieces where strength matters more than purity. The minimum platinum content for which the 'platinum' designation is permitted in the US under FTC guides.
Published May 30, 2026
Quick facts
- Metal
- Platinum
- Purity
- 85.0%
- Fineness
- 850/1000
- Common regions
- Japan, international
- Density
- 19.4 g/cm³
- Melting point
- 1730 °C
- Standard
- ISO 9202
Stamps that mean the same thing
This purity may be struck into jewelry as any of: Pt850 / PT850 / 850Pt. The mark differs by country and era, but the metal content is identical.
What Pt850 tells you
85% platinum. Used in chains and pieces where strength matters more than purity. The minimum platinum content for which the 'platinum' designation is permitted in the US under FTC guides.
How to value it
The melt value of a Pt850 piece is platinum spot price × 0.850 × 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 Pt850 or an equivalent such as PT850.
- Weigh the piece and estimate its volume — the density should land near 19.4 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
- FTC Jewelry Guide 16 CFR Part 23.7
- Wikidata Q880
* Frequently asked
FAQ
- Q. Is Pt850 the same as PT850?
- A. Yes. Pt850, PT850, 850Pt all denote the same material — 85.0% platinum. Different markets and eras stamp it differently, but the purity is identical.
- Q. How much is Pt850 worth?
- A. Its melt value is the platinum spot price × 0.850 × 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 Pt850 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 (19.4 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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