Here's a possible future project with some interesting challenges. This project really appeals to my inner geek, the part of me that loves to experiment with microprocessors and electronic components.
On the top of the box is a seven segment display, the type used in LCD calculator displays and petrol station price signs. (USA = Gas station) Turn the handle and the counter counts.
A worm gear will be used to step down the handle rotation so that ten full turns will be needed for the full count. Each segment of the display will be a hole in the card with a sliding shutter behind it. Move the shutter to one side to reveal the black, to the other side to reveal white. The seven segments can then be driven by a pack of cams in the box base driven via the worm gear.
To extend the project it would be great if several seven segment displays could be linked together so that they could count to 99, or 999 or even beyond!