Faber Castell disponent 1/22A Addiator pen slide rule 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 standard size version is the disponent (Kaufmann) 1/22 for the trader. It is made of sturdy wood with white celluloid layer with plastic angled cursor. The all metal Additiator is fully working and complete with the pen. Both are beautifully embedded in the wood. The original green sleeve is complete. Everything is in very good condition with no flaws and minimal signs of use and age. It measures ca. 30 cm or ca. 12 inches wide. Check the attached video on how to work your vintage man tool : slide rule operation instructions!