This is another Flektogon lens by Carl Zeiss Jena using the same basic lens formula first introduced in the 1950´s. All of these Flektogon lenses are retrofocus designs. This lens design is also very common for a variety of medium format lenses (for Praktisix etc.).
This lens has a half stop faster maximum aperture than the standard 1:2.8 lenses at this focal length which is helpful for available light photography. It also has a very small minimum focsuing distance of only 0.20 m.
Optically, this lens is truly excellent. It is already very good wide open and becomes really outstanding when stopped down to f/5.6 or more. If you want to use this lens you should definetely get the MC version (with multi-coated lens elements).