The 138389 serial number is in the 2nd Model range (91,418 to about 170,000) and the sight should be pinned to the barrel assuming the barrel number matches the frame. The 3rd Model (~170,000 to 242,981) had the forged front sight. Something doesn't add up with this revolver. Photo #3 that shows the left side of the barrel has what I believe to be an applied forged sight. I see an almost invisible outline of what appears to be the slot in the rib for the grafted sight. I agree with mrcvs, cut barrel with altered sight.