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Keywords: Senator John Heinz History Center - IMG 7824.JPG Exhibit in the Senator John Heinz History Center 1212 Smallman Street Pittsburgh Pennsylvania USA There were no restrictions on photography in the museum collections Thacher cylindrical slide rule circa 1890; patented in 1881 by Edwin Thacher 1839-1920 I took this photograph 2010-12-02 16 29 41 Daderot Public domain Senator John Heinz History Center Slide rules |