This is a Soviet made 85 mm Finder for the classic rangefinders (Leica, Contax and their copies). Made of plastic with glass optics.
The finder is clean and fully functional – the image is clear and sharp. It was sold as a separate accessory for the Soviet 85 mm lens – Jupiter-9 (in both LTM and Contax bayonet mount).
It is shown on a Leica IIIa (camera and lens are not included)