Zeiss Jena T 3.5cm F2.8 Biogon

I am starting to get confused by the variety of Zeiss Contax rangefinder Biogon models after thinking I had it all understood. I know that the pre-war Biogon and the post-war Carl Zeiss Jena Biogon do not fit the Contax IIa and IIIa. However, it is my understanding that on at least some post-war Jena 3.5cm Biogon models, the large convex rear element is protected by a guard ring, rather than being completely exposed as in earlier models (and on the Jupiter-12). Can anyone here verify this? Also I thought this rear element came right up to the film surface, almost touching it.

This post may answer my question:

(there was a url link here which no longer exists)

It seems to show a post-war Biogon with a recessed rear element. However this photo set shows a post-war T Biogon with an exposed rear element:

Dead Link Removed

The whole Contax II/III and later IIa/IIIa's and the pre and post war 35mm lenses is a bit of a saga. I kinda gave up. If I do end up with a 35mm lens, it may be a newish Voigt or a Nikkor. I even understand there was a post war Jena 35mm that fit the IIa/IIIa cameras. Bio...? -tar maybe.

Jeff L said:

The whole Contax II/III and later IIa/IIIa's and the pre and post war 35mm lenses is a bit of a saga. I kinda gave up. If I do end up with a 35mm lens, it may be a newish Voigt or a Nikkor. I even understand there was a post war Jena 35mm that fit the IIa/IIIa cameras. Bio...? -tar maybe.

Click to expand...

Well the Planar fits the IIa/IIIa - said to be a great lens too. I have a pre-war Biometar that fits all Contax. Neither of these lenses have a deep rear element - that's why.