i have a couple sight bases, might sell one.. and i also sell a tool that makes the installation much easier, the blued barrel, looks to be an 03 barrel, thats had the base removed, and then blued, and removed hard,
the A17 is likely a steel lot code, and might be a RIA barrel. maybe John Beardicon can narow that steel lot dowm.
might ask for the length, and the markings about an inch below the muzzle, and a picture of that area...see if the ground off the sight key.