Small correction.
That sight is not a Diana 100 sight, it is a Gehmann sight. A model 590 L.
The sight alone retails for 180 to 200 dollars sans the adjustable iris mounted on it.
The diopter looks like it has polarization adjustment and possibly diopter correction as well. You are looking at close to 500 dollars US for the rear sight set up.
gehmann.com
Retail price of the sight
Gehmann compact rear sight now available at Oberle Enterprises. Give us a call for all your Competitive shooting supply needs. 720-670-6818
oberleenterprises.com
Found the diopter as well
Iris 0.5 - 3.0mm Two polarisation filters: 1. ring eliminates reflections and controls white around target 2. ring (with stainless lugs) controls light through the sight and enables varying degrees of brightness 10 - 90 % light absorption via the twin…
gehmann.com
Retails for close to 300 USD.