2x Faber Castell dealer slide rule 1/22 1/28 Bivius 1950 Germany

2 slide rules by Faber Castell from the 1950’s. Model 1/22 disponent and 1/28 Bivius (aka super business). Both are dealer / business rules produced in the same period but with small difference, hence I offer them here as an interesting set.  Both are complete with their original case. Both are laminated wood with plastic cursors and both are in good conditions with minimal signs of use and age from normal use. They measures ca. 30cm or 12 inches long. Check the attached video on how to work your vintage man tool: slide rule operation instructions!