Everything you need to know about the Friden calculator is in this video. There is a scene with Jack Lemmon in the movie "The Apartment" working on a Friden calculator. He enters a sequence of numbers to produce the "Friden March."

My father used a large 9 column mechanical calculator to balance the books at our small dime store. I used to play with at times. When you tried to divide by zero it would go through some amazing mechanical spasms before it would spit out a "0.0".

The Library of Congress's archives include dozens of Arthur Rothstein pictures of individual workers at an "aircraft engine plant, Allison Division, General Motors" with a reference to "Detroit, Michigan." But (aside from Rothstein's photos) I can find no evidence that such a plant was in Detroit. During WWII the Allison Division of General Motors operated large aircraft engine plants at Speedway, Indiana and nearby Indianapolis, and of course other GM divisions had plants in and around Detroit - but perhaps not the Allison Division. https://usautoindustryworldwartwo.com/General%20Motors/allison.htm

[The Cadillac plant in Detroit manufactured parts for GM's Allison Division. - Dave]

In the 60's, my mother worked as a lab assistant at an agricultural experiment station, and the PhD she worked for had one of those beasts. I often visited the lab and one day after doing simple additions and subtractions on it, a decided to do a division problem. Big mistake. The machine went into gyrations while sounding like it was stripping gears. The good doctor poked his head out of his office and gave me the filthiest of looks. Later on, my mother would borrow it and haul it home so I could use it to do her taxes.

That is a Friden calculator. It adds, subtracts, multiplies and divides, all mechanically. The electricity just runs a motor that turns the gears. No floating point decimal though, so you have to know where it goes. Some versions of this calculator will extract square roots.