Zeiss's ultra-wide Contax prime — the Distagon T* 15mm f/3.5, rectilinear manual-focus glass for the C/Y mount.
The Zeiss Distagon T* 15mm f/3.5 was an ultra-wide-angle lens made for the Contax/Yashica bayonet, part of the Zeiss line built for Contax SLR bodies from the mid-1970s. It sat at the widest end of the rectilinear range and was one of the more specialised optics in the catalogue.
This is a manual-focus lens for the C/Y mount with a 15mm focal length and a maximum aperture of f/3.5. As a retrofocus Distagon design, it corrected geometric distortion to keep straight lines straight across a very broad angle of view. Other construction details are omitted here where they cannot be confirmed.
At 15mm the lens takes in a sweeping field, suited to architecture, tight interiors and expansive landscape work where perspective is part of the picture. The T* coating helped hold contrast against flare with such a wide front element facing bright scenes.
On the used market this is a scarce and sought-after item that commands high prices in good condition. Check the large front element for cleaning marks and coating wear, inspect for internal haze or fungus, and confirm the aperture blades move cleanly and are free of oil. It adapts to mirrorless bodies with a C/Y adapter.