In November 2006, the Royal Monetary Authority (RMA) of Bhutan released the new one Ngultrum note. The release, called the ‘Series 2006’, was part of a clean note policy during which the authority would mop up all the soiled, dirty and mutilated notes from circulation. See The Full Series 2006

Bhutan (2006) 1 Ngultrum (front) - Dragons

Bloomberg 3rd June 2008:-
1 USD = 42.4 BTN (Bhutan Ngultrum)