This is actually a fairly common error of this coin series, caused when a coin becomes stuck in the reverse die, and sinks an incuse image of the obverse into the next coin(s). In most mints, such errors would have to be melted and recoined, but apparently these were allowed to circulate.
It is not 100% attributable without the reverse legend, but I am pretty sure the portrait is that of Bhartradaman.
