It definitely is not an original Mithril figure. It is a conversion (modified figure) and ,I think, of very bad quality. Obviously one of the Mithril LT 13 "Harlf-orcs" was chosen as the substantial part of the figure. The arms are converted and given a different pose. An archer instead of the original swordman with shield. And, well, that base ... I will not comment.
I've only just come across this post - rather belatedly, I'm afraid - and I can confirm that it is one of several conversions produced some years ago by Jim Corless of Time Machine Productions, who was an agent for Mithril figures in the US once upon a time. The figure was never sold, but Jim fielded them in his own armies, and several were sent out as gifts to friends. In fact I think there may have been one or two different archers, but mine are all packed way in the attic somewhere at the moment, so I can't be certain.
"A worthy man, but his memory is like a lumber-room: thing wanted always buried."