Hi Stephanie and Frank,
Thanks for the additional information. In posting I was aware that my information was at best going to be incomplete (hence my qualifications),
and my hope was that those with more knowledge would contribute
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For some context . . .
My knowledge of early Zeiss Porro’s is limited to what I've been able to find on the net
In contrast, there’s a whole lot more information available in the magisterial works of Hans Seeger. His two main works on Zeiss binoculars are for:
- 1894 to 1919, aka the Blue Book (of 850 pages), see:
https://www.quicktest.co.uk/acatalog/copy_of_copy_of_Optics.html , and
- 1919 to 1946, aka the Green Book (of 920 pages), see above
Besides the price, the main limitation for many is that the text is in German
(and for information on Seeger's sources, along with the dating of units prior to 1907 by serial numbers, see Frank's comments at:
https://www.birdforum.net/showpost.php?p=3833166&postcount=39 )
Another potential resource is the 250 page ‘An Introduction to The Binoculars of Carl Zeiss Jena 1893-1945’ by Lawrence (aka Larry) Gubas
see:
https://www.goodreads.com/book/show...o-the-binoculars-of-carl-zeiss-jena-1893-1945
While it's in English it seems to be a great rarity (I’ve been searching for a copy for some time without success)
Larry was a frequent contributor the the Zeiss Historica Journal, including some useful articles on binoculars
Copies of the journal are available both at:
-
https://issuu.com/zeisshistoricasociety/docs, and
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https://www.mikeeckman.com/zeiss-historica/
The former also includes early Zeiss binocular brochures from 1894 to 1905
And the advantages of the latter are that:
- there is an index of articles, and
- the downloadable PDF’s (vs screen shots) have clearer detail
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Holger Merlitz recently initiated a thread on the optical construction of Zeiss binoculars. And I contributed what I could find out about the earliest Porros at:
https://www.birdforum.net/showpost.php?p=3960049&postcount=77
However, if either of you have information that could add to/ clarify my comments, I’m sure that many would be appreciative
John