Faber Castell 67/54R addiator slide rule sleeve 1950 Germany

This is a great transitional and unusual Faber Castell slide rule that has a double function. It is a combination of slide rule on one side and an addiator on the other side. The addiator is a predecessor of the basic handheld calculator (as is the abacus) with function that allows for quick addition and subtraction of amounts. The slide rule itself is more the predecessor of the scientific electronic calculator. This pocket version is based on the Faber Castell 67/54 and is now called the 67/54 R. It comes in the original green sleeve but it is missing the pen. The slide rule is in used condition with clear signs use and age (bumped corner and a visible crack in corner (not through). It measures ca. 16 cm or ca. 6 1/4 inches. Check the attached video on how to work your vintage man tool : slide rule operation instructions!