...the frame of the two baumuster is pretty much the same.

As far as I know in the first planning the two models were supposed to be more distinguished (like the W 110 and W 111)

Since the W 108 and the planned W 116 already covered the higher end, the W 110/W 111 predessesor ended as one model with two numbers.

To get more into the details I have to ask Michael Rohde, probably the most knowledgable person about that model.

Kind regards
Eberhard