They were Zeiss before the end of ww2.
The Jena factory was on the wrong side of the border between east and west Germany after the war. The factory continued making optics for the east German Army and export optics for everywhere else.
The postwar name was Zeiss Jena and they had access to the clear sand that made Zeiss optics so renowned. I have 2 sets of Zeiss Jena binoculars and they were considered at the time to be some of the best in the world.
Docter is the unified Germany name