Falke Air Rifle Sights
Falke Modell-80 & Modell-90 diopter rear sights.
The following pics show three Falke diopters, two of the first pattern with a half-round head dovetail clamping bolt and one of the second pattern with a "T" head bolt. The latter bolt was common to the second pattern open rearsight also.
The second pattern clamping bolt lacks the small "anti-recoil" pin wedged into the first pattern bolt heads. This was apparently designed to slot into the notches on the trigger block dovetails present on some (earlier?) rifles and absent on (later?) others.
One of the first pattern sights has a fixed aperture while the other two have adjustable apertures, accessed by turning a small wheel set into the eyepiece.
Another difference is the shape of the curved profile of the underside of the diopter block, which mirrors the rear of the 80/90 trigger block that it sits immediately above. The second pattern diopter has a flatter profile.
Lastly, the knurled eyepiece disk on the second pattern sight is much thicker than on both of the first pattern sights.