"To further develop the system, in January 1958 IBM hired Jack Kuehler to head up a team exploring Kalvar-based films. He quickly concluded that Kalvar was not stable enough to store data with the sort of reliability IBM demanded,[2] breaking down over a period of a few years and giving off corrosive gas while it did so. Kalvar is based on a diazo film and Kuehler was able to identify a similar film that would provide the reliability required, although at the price of needing to be developed in a wet lab process. He proposed a new version of Walnut that replaced the Kalvar developer with an automated diazo film developer system that developed the film in a few minutes. He was able to convince the CIA to accept this change, and the new version was announced in 1961 and delivered the next year.[1]
"The primary element in a Walnut system was a large cylindrical carousel called the document store. Each store contained 200 small boxes IBM referred to as cells, in keeping with earlier magnetic tape-based systems. Each cell contained 50 strips of film, each of these containing 99 photographs arranged in a 3 by 33 grid. In total, each document store contained images of 990,000 documents, and up to 100 document stores could be used in a single Walnut system, for a total storage of 99,000,000 pages.[1]
"A separate system was used to access pages from the Walnut system. Users would look up keywords stored on an IBM 1405 hard disk system, identifying individual documents to be retrieved. The machine produced punched cards that were inserted into the Walnut. The Walnut system retrieved the documents, copied them onto a film strip and developed it, and then inserted four such images into an aperture card. The card could be read directly on a microfilm reader, or used as negatives for full-sized printouts. (Wikipedia article on IBM 1360, accessed 10-2020).
