Hi,
you have to look for a trace (or rather the absence of it) between the 3rd and 4th reflections as the TSN-3/4 have a Steinheil design doublet with the CaF2 element (which takes the role of the crown glass here) as the back element and a crown glass (usually BaK5 - it takes role of the flint here) at the front.
Only Takahashi has so far dared to offer a Fraunhofer style doublet objective with a CaF2 front element in their FS series - and only in the early nineties after their friends at Canon-Optron (who makes the fluorite objectives for Takahashi and Kowa) had learned how to coat CaF2.
Joachim
you have to look for a trace (or rather the absence of it) between the 3rd and 4th reflections as the TSN-3/4 have a Steinheil design doublet with the CaF2 element (which takes the role of the crown glass here) as the back element and a crown glass (usually BaK5 - it takes role of the flint here) at the front.
Only Takahashi has so far dared to offer a Fraunhofer style doublet objective with a CaF2 front element in their FS series - and only in the early nineties after their friends at Canon-Optron (who makes the fluorite objectives for Takahashi and Kowa) had learned how to coat CaF2.
Joachim