Quote Originally Posted by Q.G. View Post
The fact that this configuration is rare does not mean it is wrong.
Fair enough.

Quote Originally Posted by Q.G. View Post
Nor that it is more likely to be wrong than correct.
If we would assume that sort of reasoning, anything rare should really not exist.
Whether the lens is assembled correctly is an empirical question. That said, the odds (many many published cross sections of double Gauss derivatives with outer elements convex outwards, few with an outer element concave outwards, none with both outer elements concave outwards) that it is not assembled correctly are high.

Note, however, that the cross-sections I have access to are of lenses designed before around 1970. High performance wide angle lenses designed since then look a bit strange relative to older designs, this may be true of high performance narrow angle lenses too.

I didn't assert non-existence, I asserted low probability that it is correct. There's a difference between the two.

Dirk, your images seem to show no diaphragm. Is there one?

FWIW, Dirk, I have an ex-USAF 36"/8 B&L telephoto doorstop whose cells are held together by a sort of clamp. No shutter, no diaphragm, and the cell spacing might but need not be correct. Anyway, my lens is clearly incomplete, makes me wonder whether your monstrosity is complete and its cell spacing correct.