This is the Zeiss Contax equivelent of the Leitz Visoflex mirrorbox.  Works with dedicated lenses such as the famous 18cm f2.8 Olympia Sonnar.  Also works with the Nikon rangefinder system and their fast tele lenses such as this 18cm f2.5 pictured.  Optics are a little hazy due to age but it is perfectly usable. (Note this listing is for the mirrorbox only and does not include the Nikon SP camera or 18cm lens shown in the last pic)
 
loc E9