Bhutan, 1979 AD., Jigme Singye Wangchuk, 3 Ngultrum, KM 50.

Bhutan, Jigme Singye Wangchuk (1972 AD. - ), 1979 AD.,
3 Ngultrum (38,5 mm / 28,16 g), copper-nickel, 28,28 g theor. mint weight, mintage 10.000 (?) , medal alignment ↑↑ (0°), reeded edge,
Obv.: ... / · 1979 · , crowned head facing left.
Rev.: ... / · ROYAL GOVERNMENT OF BHUTAN · 3 NGULTRUM · , national emblem within circle, denomination at right.
KM 50 .

from Nicholas Rhodes - COINAGE IN BHUTAN: http://himalaya.socanth.cam.ac.uk/collections/journals/jbs/pdf/JBS_01_01_04.pdf :
... From 1974, a number of new coins have been struck, both at Indian mints and at various foreign mints, but few have circulated to any significant extent, most having been ordered by outside agencies, and marketed internationally. In practice, coins have ceased to have any local relevance in Bhutan, and I will not list such recent pieces in this article.
The coins have been almost entirely replaced by bank notes, which were introduced in 1974.