Big Dog, very interesting.
Mine is a '91 S-class, so should be similar.
What do you mean by Red sensor on the key: RF ID? coded resistor?
My keys appear to have no RF or resistor chips, or any embedded electronics.
But I guess it could be hidden under the rubber end.
I assumed it had no such system.
I'll try the push-button right-hand locking and see if it triggers the alarm.

This is getting interesting; makes me want to pull the door lock and see what-all they have in there. I know it's not too simple, because if you try to push the driver lock down, with the door open, it won't go down - so it's pretty smart.

DG