Notes: "The K&E model 4061 5” slide rule is the shorter version of the 4071, which was the successor to the original Cox Duplex. The 4061 is unusual in that it has 320 divisions on the C and D scales, the same as a typical 10” slide rule. This makes the 4061 the 5” equivalent of one of K&E’s “F” 10” slide rules, with fine divisions. The utility of these very fine divisions is questionable (the smallest spacing between tick marks is 0.011”, and the cursor hairline would be 0.004” to 0.006” wide). This 4061 would have come from 1910 to 1920, and since the cursor is missing, probably 1915 to 1920, when the fragile all-glass cursor was in use. "
