Stuart C. Dodd. “The Applications and Mechanical Calculation of Correlation Coefficients”, in Journal of the Franklin Institute, vol 201, no. 3, March 1926, pp 337-350 in the volume of 886pp, with several illustrations, including a photo of the preliminary model of the correlation machine.  Library cloth binding, with call number on spine and a library bookplate and a few stamps on the title page, otherwise a very nice, solid copy.  $250

• “Around 1925 Stuart C. Dodd, a psychologist at Princeton University, made a simpler correlation calculator. This machine (Figure 6) contained drums on which square numbers where represented by pins of different lengths (separate pins for units and tens). These drums are the square number equivalent of the multiplication bodies as used in the Millionaire calculator. Dodd designed different versions of this device. Later development was continued by the Cambridge Instrument Co. Inc., New York, who sold these correlation machines to the universities of Harvard, Berkeley, and Chicago.”–“Correlation Machine” article in “The contribution of psychologists to mechanical computing” via google sites.