The 300/4 Sonnar was another of the Zeiss lenses that was introduced at an inopportune time. At f/4, it was a fast lens for it's length, but as it was introduced in 1940, it saw limited production due to the war.
The first batch of lenses, estimated at no more than 100 units, were finished in chrome, and were sold in the Flektaskop reflex housing mount. The second batch had black barrels with a chrome head. A change was also made to the focusing ring. This lens was also sold only in Flektaskop mount, and only about 50 are believed to have been built.
After the war, production resumed in Jena. The lens could be had in Flektaskop, Panflex or Flektometer mount.