Well, I own an 4”, f/7.5 apochromatic telescope with six lenses - to continue your listing it’s something like a “sext-tublet” and therefore it should be quite rare. But it’s rareness has another reason: The telescope is a prototype model - only a single one was produced.
It’s a TAL-100 Apolar telescope from Russia.
And .. . it’s a quite good performer: diffraction limited, very good color correction, a small touch of coma (I still tolerate the coma, for collimation of the system is quite difficult), multicoated lenses.
As far as I know a second 4” prototype was produced, but with different lens radiuses and uncoated lenses, too.
With the experiences of the pre-series model(s) the 125mm Apolar telescopes were produced, leaving back my single (?) 4” TAL-100 Apolar. So, it should be definitely a quite rare telescope ...
Edited by Andreas-TAL, 02 November 2019 - 06:12 PM.