If those barrels are marked "Royal Steel" they are fluid steel and were originally fitted to Hunter's lowest grade hammer gun, which is OK as they will work equally well on a hammerless frame. Don't know why this barrel set would have a rib inlay, which was never a feature on a low grade hammer gun; but as to engraving I suggest you duplicate the engraving pattern on the original barrel set if they exist, and if not use engraving motif equivalent to the grade stamp on the gun frame. As to changing the grade mark and serial number on the replacement barrels flats, I'd leave them as is if the gun were mine.