The W126-043 chassis 380SEC Coupe with the M116-963 motor was made between 1981 and 1983.
The W126-044 chassis 500SEC Coupe with the M117-963 motor was made between 1984 and 1985.
The W126-045 chassis 560SEC Coupe with the M117-968 motor was made between 1986 and 1992.
The W126-046 chassis 420SEC Coupe with the M116-965 motor was made between 1985 and 1991.
Prototype? No. This isn't even a W126, it's a W109 300SEL6.3 with one-off Pininfarina coachwork. Was it inspiration for the 126 SEC? How could it not be? This car was sold in 1971 however, the SEC came out 8 years later.
Aftermarket body styling by Sbarro.