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Gold hallmark numbers represent parts per thousand of pure gold. 916 means 916 parts gold out of 1000 — which is 91.6% purity, or 22 karat. 750 means 75% pure (18K), and 585 means 58.5% pure (14K).
BIS Hallmarking in India: The Bureau of Indian Standards (BIS) runs India's official gold hallmarking program. Since June 2021, BIS hallmarking is mandatory for all gold jewellery sold in India. A BIS hallmarked piece carries 5 marks: BIS logo, purity number, assaying centre mark, jeweller's mark, and the 6-digit HUID.
Why hallmarking matters: Without a BIS hallmark, you have no guarantee of purity. Always insist on BIS hallmarked jewellery and verify the HUID on the BIS portal before purchase.