I went this weekend to my parent's house. He proudly showed me his latest acquisition, which was at the same time the very first calculator he used (he's now 75 and started working at 16, like many youngster his age). It was an Odhner Original, an Swedish brand that was sold in Spain at that time. He even has the manual in Spanish, and he was able to show me how it was working. Please take a look at it.
This is a pin-wheel calculator. My father showed me how to perform an addition ( a little cumbersome), a multiplication (looks simpler but requires more rotations of the wheel) and setting it back to zero.
Take several more looks a little bit closer:
And a little slanted:
I have the manual and intend to take a look at it. With the many things happening in our lives, I do not plan to spend a lot of time learning it - I need to learn the HP 39gII, in order to set it up for the web, since it will be on sale mid june! There are things much higher in priority right now.