This round slider rule is type ALRO 100R Rietz, it comes in its complete metal case, outer box, manual and paperwork. Made in Holland in The Hague around 1960 after the patents were received. Basic model but sold far less than the 200R model that was mandatory on several Dutch higher educations. It is in close to new condition with hardly any signs of use and age. Fully functioning. Closed it measures ca 13,5 cm or 5 3/8 inches wide. Only the outer box shows signs of storage, one side is ripped so the box folds open. See pictures for details. Check the attached video on how to work your vintage man tool : slide rule operation instructions!
