Duel at the Rio Grande is a 1963 Italian/French/Spanish co-production film starring Sean Flynn.
Ramon Martinez y Rayol, a half Basque/half Castilian caballero leaves his native Spain for Mexico at the request of his mother.
She tells him that the father he was told was dead, is actually alive and living in Mexico and has asked for his son's help.
Determining that his father has met with foul play, he uses "the sign of Zorro", to lead a campaign against a corrupt generalissimo.
To avoid copyright issues,(Disney had released a compilation film of their TV series with the title, Sign of Zorro (1960)), Harry Joe Brown released the film under the less Zorro sounding title of "Duel at the Rio Grande" and had removed from the film almost any mention of Zorro.