A few 6.9's, right at the end of the production run, were fitted with ABS, by DB.
I wonder if this was one of them, or was later fitted with a W126 system.
Airbags were first fitted as an option on the W126.
I have read a magazine article of a Gullwing fitted with ABS. The propellor shaft was marked so that a laser reader could read the movement of it, and thus detect detect skidding in conjucttion with non movement of the wheels.