Mercedes-Benz 190 SL (W 121, 1955 to 1963) in the design engineering office of the form development department, March 1955. These models show development from the preliminary stage to production version, from left to right: 1:10-scale plastic model, 1:10-scale synthetic resin/fibreglass model, 1:5-scale plastic model and one of the first cars from the pre-production series