Hallmark
An official stamp certifying precious metal purity. In India, BIS hallmarking is mandatory for gold jewellery.
A BIS hallmark carries three things: the BIS mark, the purity in fineness such as 916 or 750, and a six-digit alphanumeric HUID unique to that item.
Hallmarking is compulsory for gold jewellery sold in India. Silver hallmarking exists but remains voluntary.
The mark is struck at a licensed assaying and hallmarking centre, not by the jeweller, which is what makes it independent.
When you are buying
Check the HUID in the BIS Care app before paying. It takes under a minute, names the registered jeweller and the declared purity, and is the only independent verification available to a retail buyer.
HUID
The six-character code stamped on every hallmarked Indian gold item, unique to that single piece.
916 Gold
The hallmark number for 22 karat gold, meaning 91.6% pure. The same thing as 22K.
750 Gold
The hallmark number for 18 karat gold, meaning 75% pure.
Fineness
Purity expressed in parts per thousand rather than karats. 999, 916, 750 and 585 are the numbers you will see stamped.
Assay
The laboratory test that establishes how much gold is actually in a piece.