The seller of that gun is either ignorant or a liar. It is not a copy of the BSS. Came out of the same factory, made (probably) on the same machines, but it is a different gun. Different triggers, different chambers, different barrel weight, different rib, different buttstock, different forend, different frame shape... But otherwise identical.

Larry Brown did a Miroku article in Shooting Sportsman a long time ago that included some discussion of the Monkey Ward Mirokus.