Non-Commissioned Officer Development Ribbon
From Halopedia, the Halo wiki
A Non-Commissioned Officer Development Ribbon is an award issued by the UNSC (Based on the US Airforce) to recognize those non-commissioned officers who have completed a prescribed leadership course at an NCO training school. It is seen on Captain Keyes' medals.[1]
Air Force
The NCO Professional Military Education Graduate Ribbon was issued by the United States Air Force and is awarded for completion of proscribed non-commissioned officer professional development programs. Such programs include Airman Leadership School (ALS), Non-Commissioned Officer Academy (NCOA), and the Senior Non-Commissioned Officer Academy (SNCOA). Additional awards of the NCO Professional Military Education Graduate Ribbon are denoted by oak leaf clusters.