I found this information in a paper about Ampex. Perhaps this is what you have.
"In the midst of the crash project to assist Michael Todd, George Skouras, CEO and controlling stockholder in United
Artists, approached Ampex for equipment to produce three-channel stereo sound with a fourth for surround for 20th
Century Fox’s CinemaScope process. CinemaScope used 35mm film, with reduced-size sprocket holes. The widescreen
picture was compressed horizontally on the film, and restored to a 2:1 aspect ratio with an anamorphic lens attached to a
standard 35 mm projector. Much of the hardware for both the Todd-AO and the CinemaScope project was similar. The big
difference was that CinemaScope required the development of a special adapter, nicknamed a “sandwich” which was
mounted on a standard 35 mm projector to pick up the magnetic signals from a multi-track magnetic strip along the
edge of the film. The “sandwich” had to deliver those signals flutter-free, in spite of the sprocket holes in the film. The
resulting device employed the industry-standard Davis drive.
Here's a link to the paper:
http://www.aes.org/aeshc/docs/company.histories/ampex/leslie_snyder_early-days-of-ampex.pdf