Notes: "The model 4053 Mannheim slide rule, or Polyphase Slide Rule as K&E called it, was in production from 1909 until 1972, was available in 5”, 8”, 10”, and 20” lengths, and along the way went through many changes, major and minor, in construction, scale layout, and markings. Those changes make determining the date range for this slide rule fairly easy. The K scale being on the lower edge broadly sets the date range to 1909 to 1921. The use of the “-3” length designation (indicating a 10” slide rule) in the model number started in 1911, and the metal framed cursor ended in 1915, so this slide rule was made between 1911 and 1915. This 4053 is the scarce “finely divided” version (the “F” in the model number), which has all the divisions of a 20” slide rule on a 10” slide rule. "
