XXL Alro for PTT Röntgen class room Slide rule 1960 Holland

This round slider rule is rare since it is a hughe 20×20 inch or 50×50 cm class room / demonstration model. It is the large version to the field edition I sold before, see PTT röntgen slide rule which measures 14 cm or 5 1/4″ in diameter. This slide rule has beautiful color and is marked with the name of the Dutch inventors. Made of plastic with minimal signs of use or age. Made in the Netherlands (by ALRO) around 1965 when during the cold war everyone was talking about radiation and nuclear bombs. It was made for the Dutch civil defence and the PTT was part of the dutch Government and in charge of printing and delivery. Fully functioning and in great condition. I also featured in this blog post one circular slide rules by ALRO. This exact model was also featured in the recent book on ALRO: “THE ALRO CATALOGUE” (2020), which you can find in the last picture (do notice the floor in the picture and the book on the background are the same!). Check the attached video on how to work your vintage man tool : slide rule operation instructions!