Apollo Domain/OS was a distributed environment that was the birth place of some of the technologies underlying DCE. POSIX threads and Microsoft COM directly trace their roots to this. Apollo was a big player in the development of DCE (Distributed Computing Environment) bringing in important pieces.

Many of the extensions found their way into Turbo Pascal, albeit slightly shifted.

The DISCARD procedure is an interesting twist

The UNIV keyword to suppress parameter type checking was replaced with the ability to use untyped parameters.

VOLATILE declarations were clearly leading edge.

Any interesting extensions? You tend to find a lot of those in Pascal implementations of that age to fix the shortcomings of the language.