Today's antique store find: an Addiator Duplex mechanical computer!
They were made in Germany from 1920 to the 1980s (obsoleted by electronic calculators). This one is from the '50s or later, due to "West Germany" reference in the instructions.
An amazing fact about this calculator: not only does it work without batteries, it works without access to my address book, location, and photo album! They were advanced in the olden days. #privacy#technology