Hallmarking

Katherine Seaman Jewellery hallmark tag assay office london

To ensure the authenticity and quality of our jewellery, we entrust it to the London Assay office for hallmarking. Each piece undergoes thorough testing and is then stamped with a full traditional UK hallmark.

The hallmark comprises of these five marks:

  • Sponsor's mark (KS)
  • Traditional fineness mark
  • Millesimal fineness mark 
  • Assay Office mark 
  • Date letter mark 

To legally sell items that exceed the indicated weights, they must be hallmarked as the described metal.

  • Silver 7.78g
  • Gold 1.0g
  • Platinum 0.5g
  • Palladium 1.0g

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