I read somewhere (Putz?) that Zeiss developed more sophisticated lens coatings during WWII but those lenses were mostly reserved for military applications. Coating of lenses didn't become popular in the consumer space until after WW II and I believe Zeiss held the patents for those -- later taken by the Allies as part of war reparations. Because of that Leitz -- in Germany (and somewhat ironically) -- couldn't use those proprietary coating techniques until sometime later. Now ... all this is based off memory from a posting a read a couple years ago so take it with a grain of salt, unless someone can validate it.