I didn't have much interest in this calculator until I took it apart. Modern calculators are very cost conscious and the construction tends to be flexible membranes and other non fixable things, fixed together in a non removable way.
This calculator, though, is totally different. It's a simple, basic calculator, but internally it is a set of modules that plug together. Without the case and plugged together the modules look like this:
The keyboard unplugs:
The processing unit has a single ceramic IC on it, made by Toshiba. I suspect the whole calculator design is a Toshiba one:
The display module has seven segment LEDs on it, each digit being a seaprate module.
The seven segment display modules look a bit the worse for age:
but they do all work:
The set of modules connect together well, and the connected unit plugs into the case using the battery connector as a mechanical link. A single screw then holds the case together. A really neat design.
I've got a video showing how it all fits together here: