I remember seeing pictures of this thing in newsreels… not on their original screenings of course.
The Differential Analyzer was MIT’s first computer, built by Vannevar Bush and his students in the early 1930s.
It looks like a table full of car transmission parts… a long glass-covered table with rods running along its length. It is entirely analog- values are stored by positions of rotating gears; there are no cams or ratchets that I remember.
The user interface is a graph- to input values the operator moves a stylus arm to different points on a graph, and the machine outputs another graph.
Web link of note: MIT Differential Analyzer
(At http://web.mit.edu/mindell/www/analyzer.htm)