Just this past weekend I attended a Chicago MBCA event at a prominent long time MB dealer where Bill Knauz gave the background stories of his collection. Included, side by side, were a W111 3.5 Coupe, W108 280S, and a W111 Cabriolet 3.5 with original paint. The attached photo shows the differences between low/high grille.
Other cars in his collection included a W113 w/16,000 original miles, an unrestored 300SL Gullwing and 300SL Roadster.