My friend Hakan from Istanbul, wrote:

“Naim, very interesting but daimler-benz hasn’t got a “success” history web site provided with pictures for mercedes. But I could that mode in another webpages.
http://www.autoevolution.com/cars/mercedes-benz-s-klasse-ponton-w180w105w128-1954.html
http://www.mbzponton.org/pax058/people/photogallery180.htm
… according web pages this model is a Mercedes S-class W128 Ponton.it has three types;hard top,coupe and convertible.”
[ source: http://www.malaysianwings.net/forum/index.php?showtopic=13388&view=findpost&p=240951 ]

Based on Hakan’s pointers, I google further to reveal:
http://en.wikipedia.org/wiki/Mercedes-Benz_W120/121

Now I’m convinced that the Merc I had joyful rides in the 60s was model w121.110, the ’190D’ – I remember the badge well.

Thanks again, Hakan!