See  — another University of Texas related source — "Sgt. Lopez was also greeted in Mexico City during his pilgrimage to the Basilica. He was welcomed by President Avila Camacho and was also awarded Mexico’s highest military commemoration, la Condecoracion del Merito Militar."  This was a WWII award, so another source, unrelated to information about Herrera indicates that the Mexican  Military Merit decoration is the highest medal. —