Help with replacement barrel, M1 Carbine

[ob'98]

If this is a new barrel then the sight is not original to it. It's a used Underwood sight and the barrel looks like it's been sand blasted and the reparkerized. Are there any markings on the barrel flat at all like the letter H?

Thanks Bruce for responding and trying to help. There is nothing stamped on the barrel anywhere except what I posted and that is on top of the breech area. Looking at that again I believe it is a D instead of an O. If carbine barrels were needed and some were made as replacements, wouldn't they be assembled ready to install at the field level Armorer? Would that account for the front sight being installed along with the band? It looks to me like the band had to be put on first, before the front sight. What about the tag in the packaging? I could see also the packaged part was the basic barrel and whoever bought it installed the band and sight? Thanks again and I look forward to more input. PS: I put a .30-06 bullet in the muzzle and there is about 3/16" bullet still exposed so there isn't much muzzle errosion, right?