Determining Mean Effective Pressure from indicator diagrams
Notes: "This planimeter was designed for one job only: determining the mean effective pressure of steam engines from indicator diagrams. The scale is calibrated for six different weights of springs in the indicator. This is a completely self-contained system, with the planimeter, the scale, a holder for the diagram, and even a grippy card pad for the planimeter tracing wheel to run on. Ascroft's patent was granted in 1919, this one says ""Patent Applied For"", hence ~1917 for the date."