This round slide rule is marked ALRO Syst 600E, comes in it’s complete metal case. Made in Holland in The Hague around 1950 after the patents were received. Rare Electric model in good working condition with signs of use and age. Fully functioning. Closed it measures ca 13,5 cm or 5 3/8 inches wide. See pictures for details. Check the attached video on how to work your vintage man tool : circular slide rule operation instructions!
