From what I understand (according to the USA 1984 Mercedes sales brochure) that the driverside airbag was an option beginning on USA models beginning in 1984 and was only offered on the 300SD, 380SE, 500SEL and I think even the 190E and 190D. It was not offered on the 300D, 300CD, 300TD or 380SL. Also an option in 1985. I think it also mentioned ABS optional in 1984 as well- not sure of the first year of that.

Airbag (driver) standard beginning in 1986 (USA).