The older mogs have air over hydrualic brakes and mechanical parking brake. The brakes are air boosted but other than that are standard hydrualic brakes and are exempt from air brake endorsements. The endorsement mainly deals with how to handle the brake system when some part of it has failed, if the air system on an older mog fails it makes no difference to the brakes other than the pedal is more difficult to press.
SBU type mogs have a air powered parking brake, you need something like 12bar in the tanks to release the brakes. I am not sure on the legal status on these systems but nobody I know with an SBU mog has an endorsement.
You don't inherit the world from your parents, you borrow it from your children.
1979 Unimog 416 Expedition Camper
1974 Unimog 421
2004 Dodge Ram 2500, 4x4, Double Cab, Cummins Turbo Diesel
2006 25' Airstream International CCD
2009 Harley Davidson
Sugarloaf, Boulder, CO