This is a fully 3D printable mechanical tally counter thing. The button function isn’t perfect but the numbers scroll up fine. Not too hard to print it but you may need to file down parts to get nice gear meshing.

Watch this short video to get an idea of how it works. I should note that the STLs I uploaded here are a little different than what I printed but should still work. Instructions:  –  The intention is to have the button increment one digit at a time and have the knob, when pressed turn the numbers either way. The knob works great but the button needs some work. –  You need to print TWO carry gears. One of everything else. –  The three number wheels need some sort of support and maybe the case and cap as well. –  The button spring part may not print exactly as it the STL looks. It’s a mesh problem but it’s probably better the way it is. –  I have fixed the jog Knob file as of 7/26/15. Some slicers had sliced it as a solid piece.