Originally posted by Thomaspin
Maybe the factory added the trunk key-activated central locking in 1989 or 1990 - my 560SEL is a 1990.
I believe it was added to the 126 for the 1985 model year. I believe it's essentially the same system on the 124 which was introduced to the US market in the 1986 model year.
I don't know if the system was changed for the later 124s that may or may not have the IR keyless entry system.
Passenger side key activation was added in 1985. I don't know if trunk activation was added in 1985 as well.