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The film, which was shot in Mexico in both English and Spanish-language versions, had the working title La bestia de la montaa and was released in Mexico City on April 18, 1957 as El monstruo de la montaa hueca. In the opening credits, following the acknowledgment that the film was photographed in CinemaScope and that color was by De Luxe, a title card reads "Introducing the new Nassour Regiscope process Animation in Depth." Although a November 1954 news item in Daily Variety stated that Regiscope, which was invented by Edward Nassour, had been used in Nassour Studios' "previous feature, Ring Around Saturn," all other sources state that the process was first used in The Beast of Hollow Mountain, and no additional information about Ring Around Saturn has been found.
According to news items and studio information, Regiscope, a combination of the words "register" and "scope," was developed by Nassour to "control miniatures and inanimate objects in absolute registration...prior to the actual photography." A studio information sheet submitted for Academy Award consideration went on to explain that miniatures that were to be inserted into the action, in this case the Tyrannosaurus Rex that was the "beast" in the picture, were placed "on a turn table and turning at a normal speed, for the correct timing and tempo of the miniatures with a strob. [sic] light, showing only the miniatures in the front position," thus enabling the technicians to make adjustments as needed. A news item stated that the Tyrannosaurus Rex was shot only three inches from the camera.
Following the opening credits, an offscreen narrator relates the story of a beast said to live inside a hollow mountain in Mexico, adding that men and cattle disappear "but perhaps these are only tales-tales told by a simple people." Although reviews and copyright refer to the "Beast" of the film as a dinosaur, within the story, it is only called a beast.
Nicolas De La Rosa, who is listed on Hollywood Reporter production charts as the film's soundman, is credited, under the name Nick Rosa, with "sound dialogue" in the onscreen credits. Although only Jorge Stahl is credited onscreen as the film's director of photography, early Hollywood Reporter production charts list Henry Sharpe as the photographer, then list both Stahl and Sharpe.
Contemporary news items state that the Nassour brothers, William and Edward, had originally struck a deal with Twentieth Century-Fox to distribute the film. Various news items state that Nassour Studios would share producing credits on both the English and Spanish-language versions with Pelculas Rodrguez, S.A. of Mexico and that Edward Nassour and Ismael Rodrguez would also share a joint directing credit on both versions. The onscreen credits state that the film was "Co-produced with Pelculas Rodrguez-S.A." and lists both Nassour and Rodrguez as directors.
According to news items and copyright records, the film was shot in and around Cuernavaca and Tepoztlan, Mexico. Although news items also state that The Beast of Hollow Mountain was shot at the Estudios Churubusco in Mexico City, most of film's sequences appear to have been shot on location. A January 14, 1955 Hollywood Reporter news item stated that actor J. P. "Bill" Catching had left the previous day to join the cast on location in Mexico, but his appearance in the released film has not been verified.
According to information in copyright records and reviews, the film marked the motion picture debut of child actor Mario Navarro, who portrayed "Panchito." Actor Guillermo Hernndez, who was also known as "Lobo Negro," was listed under that name in some reviews. Copyright files also add that the Aztec festival of Mahvatl, which is shown in the wedding sequence, had never before been shown onscreen.