Uh, guys.....
A Ghost Ring sight is a peep sight with a press agent. It's located near the eye.
My "Deer" 870 has that very bbl on it.I had a Williams Receiver sight mounted,removed the rear sight from the bbl, and then sighted it in. Yes, I do have the sight base still on the bbl, but it's not in the sight picture and causes no probs. The aperture goes in for bench work, comes out for hunting, "Practical" and HD.
A peep sight has to be close to the eye, which looks not at the peep but through it.
HTH....