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 67/54b (see manual in German) and is now called the 67/54 Rb (see slide rule). It comes complete with the pen and the original blue leather sleeve (for RS company) sleeve that has a loop to store the pen safely inside as well as a working zipper with Faber Castell logo. Very nice set in very good condition with only signs of normal use and age. 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!
