After having more time to consider this contraption I believe there is no way it could function, as a true aperture sight does, to sharpen focus and extend field. The hole in it is simply too big, and the device is too far from the eye. It would never do anything to help aging eyes focus on anything useful to a shotgunner.
Actually, there is a type of aperture sight called a ghost ring sight which has a large aperture. They are primarily used for hunting because they are much faster and easier to acquire the target in hunting situations such as running game or low light. They are not as precise as a target aperture, but the eye naturally centers the front sight bead in the center of any size aperture, so they tend to be more precise than many standard open sights. The position of this "sight" is not much different than many tang mounted sights. And it does provide a longer sighting radius than a barrel mounted open sight would. Also, an aperture sight with a large enough hole helps aging eyes to focus on the front bead. Focus on a small distant object, then look at the same object through a pinhole poked in a piece of cardstock to see this effect.
As Miller noted, it would require a top lever system that returned to center so it wouldn't gradually change windage as the locking bolt surfaces wore over time.
