Interesting photos of mechanical calculators from the 1960s at Kevin Twomey’s web site. Here’s a sample:
There’s also a pretty cool, short video about the guy who is collecting these.
The lengths we went through to do math — even simple add and subtract — was amazing. The side views are particularly cool. There must be thousands of gears, levers and switches that make these things work. In the video he said that one of these machines could cost upwards of a $1000 in 1960s dollars (around $7000 today) and these were the pinnacle of technology at the time.
The collection belongs to Mark Glusker, who actually has even more information on his own web site. One of the things I find interesting about these machines is the button locations. On electronic pocket calculators that layout was standardized. But in the mechanical calculator days there was a ton of experimentation.
The iPad, by comparison, can do a lot more with a lot less parts. Of course try fixing an iPad yourself. You can’t. But if you were mechanically inclined you can easily fix one of these calculators.