is there some one who knows about this. never seen one before on the cylinder is stamp uma f model 90 its a milbro but the was no sights on it . other milbro parts i guess will fit . the barrel is 14.55mm with a thread hole and on the barrel breech there are 2 holes 1 threaded and a small hole drilled through the side for a pin . i guess this is from the back end of milbro production.