The Fisheye Distagon 16mm f/2.8 is an ultra-wide-angle lens manufactured by Carl Zeiss Oberkochen for the Contarex system, featuring T* coating.
This is an extremely rare lens, with only 150 units sold in 1973.
It has an optical construction of 8 elements in 7 groups.
The lens incorporates a turret filter system, housing four built-in filters: UV, orange, yellow, and blue.
The measured weight of the lens is 475g.
A true rarity.

There are two small scratches on the hood, which also serves as a lens guard.
Minor signs of use can be seen on the silver helicoid band, but overall, the exterior is in very clean condition — highly suitable for a collection.
All functions operate properly.
The helicoid has a slightly firm feel, but since this is an ultra-wide-angle lens where frequent focus adjustments are rarely needed, it should pose no practical issues (optional paid servicing is available upon request).
The front element shows two or three very faint wiping marks.
Under strong LED light, the inner elements reveal slight coating deterioration or tiny dust particles, though none of these are expected to affect image quality.
Some minor aging is also visible on the built-in filters.
Sample images are available in our Test Shots Gallery.
As expected from a fisheye lens, it offers a playful and enjoyable way to capture space creatively.
The included front cap appears to be from a Yashica/Contax F-Distagon and is made of soft plastic.