19D is your Cav enlisted man...trooper. Cav Officer 19C. Armor Crewman 19K, Armor Officer can be 19A or 19B and an Armor Senior sergeant is 19Z

Not true, if hes a Cav Officer, like i was, his alpha/numeric MOS is 19C. Enlisted man (trooper) is 19D. As u gain proficiency in specialized areas the designation grows.