I'm thinking possibly Naval Special Warfare
NSW stands for New South Wales.
It is not a military custom it's a military command, 'stand at ease' means to relax from the 'stand to attention' command.
Depending on how it's used, it could stand for "Military Specification", meaning the ability to withstand shock, dust, or harsh environments.
Military Specification
MPO stand for Military Police Officers.
Broken Hill Proprietry BHP started in Broken Hill in far western NSW.
Doctor
It is about 92km from Cowra NSW, Australia to Cowra NSW, Australia by car.
It is the military term for a 'search and rescue dot.'
nsw
At military "attention".
The Virginia Military Institute!!!!!!