the krags went through IRAN numerous times. More times than we generally realize. Originaly the receivers were case hardened, Once case hardened it can not be done again. When the were IRAN'd they received bluing and there is indeed a spot at the inside of the lunchbox/receiver, generally diagonal, that the bluing missed, presumably because of how that part was held in the bath (my presumption). I will post a photo if my 1898 that was IRAN'd when I have a chance.