Can someone axe him to measure the glass from side to side??
I did this when this ad was first brought to our attention. His response to me was that it was 16cm 'across the tube', slightly different than his initial wording of 'across the glass'. As noted previously, the left side of the cell in the closeup picture is missing, as this would have the 'Dia.' marking on it, resolving the issue once and for all. Considering the other optical equipment he is selling, I doubt the claim of his total ignorance, and feel he is inflating the size of the scope by careful mis-wording and ommision.
He could probably get many reasonable offers with a complete and proper list of specificatiions, a history of ownership, etc.
My Dad has a Zeiss catalog that shows all of their production models from the early 1900s, and probably earlier. I will email the link to him and see if it can be identified.
One thing I must admire about this fellow, however...currently, he owns the scope...and I don't.