This is the Otis King model K, type C with serial number A1658 guesstimating 1970’s. A great piece of calculator history. It comes in a full set with original box and manual and plastic insert. The cylindrical shape allows for 2 (414/423) very long scales (scales are 165cm or 66 inch) which gives the user a high accuracy for only the basic calculations (multiplication and division). This heavy metal slide rule is complete with hardly any signs of use or age and is still very shiny. It measures ca. 15 cm or 6 inches long when closed. Check out the attached video on how to operate a vintage slide rule!
