During the earlier days of the partitioning of Germany, the Zeiss group in the American zone was still not quite up to speed, and had to rely on the products and technology of the original works in the Soviet zone. Lenses from Jena were supplied not only to camera manufacturers in Dresden but to Stuttgart, and other companies as well. I have a copy of the lens catalogue from Jena, from 1954 I think, listing versions of lenses supplied to various camera manufacturers. In the east, they included Certo, Ihagee, KW, Balda (to be renamed Belca as Balda re-established in Bunde), Primar (Curt Bentzin), Welta, and Zeiss Ikon Dresden. In the west, Arnold & Richter (Arri), Berning (Robot), F&H (Rollei), Linhof, and Zeiss Ikon Stuttgart. It also listed the Flektoscop mirror housing for the Contax, and of course, later on, Jena developed the Flektometer which offered unreversed finder image, which neither Stuttgart nor Oberkochen could achieve.
This cooperation between the Zeiss companies across the political railroad track carried on until the new establishments in the west gradually got up to speed with developing their own technology and production facilities.