Film "S" is a film used by motion picture professionals for sound recording, an use which requires very fine grain and ultra high definition. This sharpness is guaranteed by a special anti-halation layer located between the film's base and the emulsion layer, while its usually in back layer for ordinary films.
Film is in ISO 50, with 36 exposures.
Data sheet is available here : http://filmwashi.com/datasheet/S_en.pdf