1. This rule was produced to facilitate the calculation of size and stress calculations for spring manufacture.
2. As it was produced for a specialised market the values of some parameters used are assumed to be readily understood and are not explained in the manual. For example E, the coefficient of elasticity, and G, the coefficient of rigidity.
3. Most of the scales are logarithmic, which means that a normal slide rule could have been used instead of those scales, but a few are not (correction for coil curvature, for example).
4. A copy of the instructions can be found here.