wear the beret, become the fantasy
the premise is already doing a lot: a teenage boy, too young to enlist, who becomes a super-soldier through magical powers. super green beret was a short-lived comic book, lost to the ages, that reads slim little twink wants to be a muscle gay. the abbot specifies that the magic cap can only transfer to someone "young and noble by nature" and works "only while wearing the glowing beret." it is pure talismanic transformation fantasy. the object is basically a magical accessory that turns adolescence into hypermasculinity.
tod becomes all grown up and later changes back and tells his uncle to keep it quiet. that secret double life thing is very superhero, yes, but it also overlaps hard with queer fantasy stuctures. think private self/public self, forbidden object, adult masculine ideal, and an impossible body. the comic is selling the 1967 boyhood militarism by being brave, patriotic, and a green beret, but it becomes so exaggerated, so body-fixated, so costume-based, that it accidentally wanders into gay iconography wearing combat boots.
the magical beret is basically a butch fairy godmother.