Understanding Jewelry Hallmarks: What Those Tiny Stamps Mean
A guide to reading jewelry hallmarks — purity marks, maker's marks, and assay marks. Learn what the stamps on your jewelry mean and how AI can help identify them.
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Key takeaways
- Hallmarks often reveal metal purity, maker information, and sometimes origin or date clues.
- Numbers like 375, 585, 750, and 925 are among the most useful quick signals when identifying jewelry.
- Close, well-lit macro photos make hallmark detection easier for both humans and AI tools.
What Are Jewelry Hallmarks?
Hallmarks are small stamps or engravings found on jewelry and precious metal items. They indicate the metal's purity, the maker, and sometimes the date and place of manufacture. Reading hallmarks is one of the fastest ways to understand what your jewelry is made of.
Common Gold Hallmarks
- 375 — 9 karat gold (37.5% pure gold)
- 585 — 14 karat gold (58.5% pure gold)
- 750 — 18 karat gold (75% pure gold)
- 916 — 22 karat gold (91.6% pure gold)
- 999 — 24 karat gold (99.9% pure gold)
You may also see 10K, 14K, 18K, etc. in the US, or ct / kt abbreviations.
Common Silver Hallmarks
- 800 — 80% pure silver (common in European antiques)
- 925 — Sterling silver (92.5% pure)
- 950 — Britannia silver (95% pure)
- 999 — Fine silver (99.9% pure)
Common Platinum Hallmarks
- 850 — 85% platinum
- 900 — 90% platinum
- 950 — 95% platinum (most common for jewelry)
- PLAT or PT — also indicates platinum
Other Marks to Look For
- Maker's Mark — A unique symbol or initials identifying the manufacturer or designer
- Assay Office Mark — Indicates where the piece was tested (common in UK, European jewelry)
- Date Letter — A letter indicating the year of manufacture
- Country of Origin — Some countries require origin marking
Where to Find Hallmarks
- Rings — inside the band
- Necklaces & Bracelets — on the clasp or near the clasp
- Earrings — on the post or back
- Brooches — on the back, often near the pin mechanism
How AI Helps
Hallmarks can be tiny and hard to read, especially on antique or worn pieces. Jewelry Expert by GradFlowLab uses AI to detect and identify hallmarks from your photos, even when they're partially worn. The AI can identify:
- Metal purity from hallmark numbers
- Known maker's marks
- Period-appropriate marking patterns
This works especially well when you photograph the hallmark area clearly and in good lighting.
Tips for Photographing Hallmarks
- Use your phone's macro mode if available
- Clean the area first — polish lightly with a soft cloth
- Use bright, angled light to catch the engraving
- Take multiple shots at different angles
- A magnifying glass held between your phone and the hallmark can help
Download Jewelry Expert on the App Store to try AI-powered hallmark detection for free.
Frequently asked questions
What does 925 mean on jewelry?
925 usually means sterling silver, which is 92.5% pure silver and one of the most common silver hallmarks.
Where can you find a hallmark on jewelry?
Hallmarks are often inside rings, near necklace or bracelet clasps, on earring posts or backs, and on the reverse side of brooches.
Can AI read worn jewelry hallmarks?
AI can help interpret partially worn marks when the photo is sharp and well lit, though severe wear may still require magnification or professional inspection.