Though the instruction manual is undated, details such as the November 1956 drawing dates provide clues about creation and publication dates.
Beckman Instruments' analog computers were being produced by their Berkeley Division as early as 1953. The company produced analog computers -- also called automation, data reduction, or data handling systems -- for the petroleum, aerospace, and defense industries. Beckman Instruments eventually stopped producing these systems after their cost and the time required to customize them kept them from being widely adopted.
Hussey, Joseph L., and C. D. Finnell. “EASE, The New 1100 Series, A Discussion of Design Theory and Operating Techniques,” n.d. Beckman Historical Collection, Box 121, Folder 62. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/zp38wc72r.