"Captain from Castile" with Tyrone Power is set during Cortez' conquest of Mexico - a little early for the period (beginning of the 16th century, rather than the last quarter), but the costumes are really closer to mid-to-late century. Most of the Conquistadors are wearing morions (and not a sallet in sight); this was must be one of those films that gave people the impression that it was particularly a Spanish helmet. Nice scene of the Conquistadors firing a tiny cannon (ala the Wargames Foundry gun).