Ouch, People,
No !!
The W107 softtop (frame) certainly does not fit on the W113 and vice versa. At least they're definitely different. Just look at the different sizes and shapes of the door windows! Maybe the one or other part and most likely the screws are interchangable but everything else is not.
It is most likely that one of the preowners retrofitted an aftermarket softtop canvas custom-made with three instead of one rear windows.
E.g. Bernd Meyer-Brockel of the German SL-Club Pagode has such a softtop canvas. But (very few) others have too.
Best,
Achim
(Magdeburg, Germany)