Gombo: It is the same shell as the Euphoria. Mendo left off the last part of the naming process:
744E = 7 person, 44 jets, E for Euphoria
641R = 6 person, 41 jets, R for Reward
520M = 5 person, 20 jets, M for Mirage
319S = 3 person, 19 jets, S for Spirit