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Pastoria is one of several new characters created by L. Frank Baum for the stage version of his story. He is the true ruler of Oz, whose throne was usurped by the Wizard. In the stage story, he is blown back to Oz by the same cyclone that captures Dorothy, and manages to regain his throne.
In this photo Pastoria is wearing a costume from the first act. He's disguised as a circus performer, and posing with the Cowardly Lion. The Lion was played by Arthur Hill (presumably inside the costume), and was nothing like the Bert Lahr tour-de-force in the MGM film. In the stage show, he doesn't speak, and plays a fairly minor role.
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Several men played Pastoria (technically he's Pastoria the Second, as noted in the caption) through the run of the show. Judging by the dates, this could be Owen Westford, who was the third actor to play the part - or it could be Arthur Larkin who was touring with the second company of the show.
The two characters can be seen in the center of this picture from the Poppy scene.