This cutaway demonstration Curta is by far the most expensive collectible I've ever purchased.
You can see the bits moving around inside when you use it.
You can see the bits moving around inside when you use it.
The Curta calculator is a marvel of engineering made by a guy who developed it while imprisoned by Nazis.
You specify numbers on the side and spin the handle up top to add them. You multiply numbers by specifying one number on the side then spinning the handle and rotating the collar.
Hard to describe via text. But there are lots of YouTube videos about it.
This particular model is special because it's a cutaway model meant for demonstrating how it works internally. It's a rare version of an already rare calculator and I absolutely love it.
The Curta feels so tactile in the way it works. You can feel the numbers being added when you rotate the handle and feel the zip of the mechanical parts interacting.