This is a Soviet made 35
mm Finder for the classic
rangefinders (Leica, Contax and their copies).Made of plastic with glass
optics. It was sold as a separate accessory for
the Soviet 35 mm lens - Jupiter-12 (in both LTM and Contax bayonet mount).
I wish I could say more about
this piece. It does not have brightlines (like the Leitz SBLOO finder),
but the image is very clear and contrasty and you do not have to pay $400
or so for it. It is shown on a Leica IIIa (camera/lens are not included).
The finder shows use and age, but it is fully functional.