If you are buying gold coins on Dhanteras and around Diwali, then it is critical to buy it from a seller or jeweller whom you trust fully. This is because hallmarking of 24 karat gold coins, bullions, bars is not mandatory as per law. Hallmarking is mandatory only for gold jewellery and artefacts. Gold jewellery hallmarking is mandatory for 24 Karat, 23 Karat, 22 Karat, 20 Karat, 18 Karat and 14 Karat purities as per law.