The Bhutanese ngultrum was first seen in 1974, when it replaced the Indian rupee at 1:1. Tikchungs were backed by rupees and were used as currency until the early 1970s. Due to an inability to properly back the Tikchungs with rupees, they were phased out and rupees were kept as the main currency until 1974. The name for the coins changed from chetrum to chhertum in 1979 when new coins of the same value were issued. As of 2008, the ngultrum can be interchanged with the Indian rupee, and Indian banknotes and coins freely circulate in Bhutan.