Awesome. I'd love to know more about instrument making techniques of the era -- especially for precisely calibrated analog computing applications like this. I know that by the 1890s machine tools were commercially available (e.g. Brown and Sharpe Manufacturing were incorporated in 1868 and were operating earlier[1, preface]) but presumably precision instrument makers evolved from clockmakers -- using hand tool techniques perfected much earlier. (Obligatory link to ClickSpring [2])