Hi Rick,
Don't know where you got the info that the mirror on the pic is for the 113 chassis - maybe it was from an ebay seller ...
... as those individuals often tell and sell you "
everything" being correct for a Mercedes 113 SL as long as they can make (more) money out of it ...
Ok, clearly that mirror pictured by you is not original for our pagodas, only the commonly known ones (early & late style).
However, in some countries side rearview mirrors were not common when our cars were new, e.g. in France.
When the SLs were new in the 60ies they were delivered by MB to these countries without door-mounted rearview mirror.
At a certain time point it became also the law in those countries to fit a mirror - and just a(ny) generic part was used instead.
This is a very common view on (ex-)French cars.
Best,
Achim