Yep, that discoloration towards the end of the slide is where James Hoag welded a 1"section of another Colt .45 auto slide. Years back, Bar-Sto made 6 " barrels, but nobody made 6" slides. I believe that Jim Clark was the 1st to come out with a long-slide but Hoag made them more famous. James Caan had one in one of his movies. Don't know if it was a 6" or a 7" long-slide. James told me one day that he thought it was a 6" in the movie.