Zeiss has licenced other manufacturers to produce their designs right from the very early days. I have a "Zeiss anastigmat lens", manufactured by Ross of London in about 1890! The labelling is totally honest, it states that it was manufactured by Ross, but many Zeiss lenses over the years have been manufactured by many other companies under licence without the labelling being quite so transparent.
More recently Yashica has produced Zeiss lenses and who really knows where the lenses on Sony and Nikon products are actually made?
And now, Cosina...
Except I don't think it is that simple. Yashica had it's lenses made by a huge Japanese optical manufacturer called Tomioka opitical. Eventually Yashica aquired Tomioka and later Kyocera aquired Yashica. Yashica has now pulled out of traditional camera manufacture but AFAIK the former Tomioka plant is still going strong as 'Kyocera optec'. Zeiss certainly had a big connection with Kyocera/Yashica in the 1990s and I suspect Kyocera optiec in Nagano is probably where the Zeiss lenses for most Japanese cameras (including the modern Contax) were made.
I once read that Minolta is the only camera manufacturer in Japan that makes it's own lenses. If that is true, that would mean all the others buy them in from elsewhere. Including Cosina - from who, I wonder? IF it is true, that is...
And the situation now? What is the relationship between Kyocera and Carl Zeiss Japan and Zeiss Ikon? And is there one between Cosina and Kyocera?
I have absolutely no idea!!! :confused:
But what would be an authentic Zeiss lens anyway? One made in Obercocken, Gurtingen, Halbergmoose, Aarlen or Wetzlar?
Or Jena or Dresden or Stuttgart?
Or Nagano or Tokyo? :confused:
I reckon if it is a Zeiss design and quality control is high enough for Zeiss to be happy to stamp their name on it then firstly it doesn't matter, but secondly, we may never know for certain where a lens has come from anyway!
And it isn't just lenses: What is an Audi if not a Skoda with a more expensive badge on the bonnet?
(And they are both owned by Volkswagon !!

)
Just my thoughts
Steve