Hallmark consists of 3 symbols as per attached picture. Before purchase the gold you should ensure the purity of gold. Check the below mentioned symbol.
Symbol-1 is BIS logo
Symbol-2 is purity and fineness
Symbol-3 is HUID
Check the hallmark sign that consists of three things -- The BIS (Bureau of Indian Standards) mark denoted by a triangle, the caratage (22K915) showing the purity, the mark of the jeweller and that of the AHC. 2) You can ask the jeweller to show his BIS licence.